2.1. Theological and classical antecedents: dominion, stewardship and equity

Discussions about obligations across generations have long been connected to questions concerning the extent of human responsibility for the natural and social world. Within the Western intellectual tradition, one influential strand derives from interpretations of Judaeo-Christian scriptures, which contain both anthropocentric and stewardship-oriented depictions of humanity’s relationship to the environment. In Genesis, humanity is instructed to ‘be fruitful, and multiply, and replenish the earth, and subdue it: and have dominion over the fish of the sea, and over the fowl of the air, and over every living thing that moveth upon the earth’, a passage often cited to support an expansive conception of dominion.Footnote ¹³ At the same time, Genesis also limits human authority in the prohibition concerning the Tree of Knowledge, and theological commentary treated such limits as imposing responsibilities regarding the use and preservation of creation. The narrative of ‘original sin’ has been used to illustrate early conceptions of burdens transmitted across time.Footnote ¹⁴ These texts articulate two themes that recur in later legal doctrine: that power over resources is conceptually distinct from absolute ownership; and that wrongful acts or excessive use by one generation may impose lasting burdens on those who follow. Both themes reappear, in secular form, in modern attempts to cast present generations as trustees or constructive trustees of ‘inheritance’.

In classical legal philosophy, the concept of equity was developed most fully by Aristotle, who conceived epieikeia as a corrective to the rigidity of formal legal rules.Footnote ¹⁵ Although not directed toward future generations in a modern sense, his discussions of moderation and restraint have been interpreted as anticipating later ideas about responsible resource use. Drawing on Plato’s Laws, Aristotle suggested that a just person may be ‘satisfied with less than [their share] even though [they have] the law on [their] side’, indicating that the equitable exercise of legal rights may require forgoing the full extent of one’s entitlements.Footnote ¹⁶ This emphasis on voluntarily foregoing lawful but excessive gain for the sake of the community foreshadows the later use of equity, culminating in the constructive trust, to police the retention of benefits where strict legal rights would otherwise permit harmful outcomes.

2.2. Roman and medieval traditions: patrimony, res communes and stewardship

Scholars such as Benke and Meissel note that the prodigus provisions, which restricted the capacity of spendthrifts, were designed to prevent the dissipation of family property and safeguard the economic interests of heirs.Footnote ¹⁷ Roman public law’s treatment of certain resources as res communes, held in common for public use, has likewise been read as a precursor to modern public trust ideas, even if it did not develop a fully-fledged fiduciary framework.Footnote ¹⁸ Charles J Reid observes that medieval discussions of natural rights drew upon both biblical and Greco-Roman sources, refining concepts that later informed Western legal thought about inheritance, stewardship and the transmission of obligations across time.Footnote ¹⁹ Thomas Aquinas played a central role in this synthesis. In his treatment of natural rights and familial duties, Aquinas emphasised the responsibility of the paterfamilias to preserve resources for his descendants, describing this obligation as ‘quod est thesaurize’.Footnote ²⁰ Reid notes that thesaurizare means ‘to build up treasure’, capturing the expectation that parents would limit present consumption to secure the welfare of future heirs.Footnote ²¹ These Roman and medieval materials provide an early jurisprudential vocabulary: patrimony, common things and stewardship, which modern law reworks in terms of trusteeship and equitable constraints on ownership.

2.3. Early modern thought: non-waste, social contract and transgenerational compacts

In the early modern period, questions of intergenerational responsibility reappeared within broader debates on natural rights, property and political authority. Locke’s writings are frequently cited as anticipating formulations of intergenerational obligations.Footnote ²² Weiss, for example, draws attention to Locke’s assertion that a person ‘has an obligation not to take more fruits of nature than he can use, so that they do not spoil and become unavailable to someone else for use – i.e., an obligation not to waste the fruit of nature’.Footnote ²³

Debates surrounding the French Revolution developed these themes, particularly in the contrasting positions advanced by Edmund Burke and Thomas Paine. Both exerted influence on Anglo-American constitutional and political thought and, indirectly, on later legal accounts of intergenerational duty. Burke famously described society as a contract ‘between those who are living, those who are dead, and those who are to be born’, insisting that the living are ‘life-renters’ who must not waste the inherited ‘fabric of society’, and treating obligations to past and future generations as integral to constitutional order and legitimate institutional change.Footnote ²⁴

Paine, by contrast, rejected the authority of the dead over the living, arguing that each generation is entitled to remake its political institutions, a tension that foreshadows contemporary debates about democratic self-determination and long-term environmental commitments.Footnote ²⁵ By insisting that each generation retains the right to reconfigure its institutions, he highlighted the democratic objection that any strong intergenerational obligation may unduly constrain the political self-determination of those currently alive. Modern courts confronting climate and environmental litigation frequently navigate this same tension, balancing claims framed in the language of intergenerational equity against concerns about institutional competence and democratic legitimacy.

2.4. Anglo-American reformulations: usufruct, inheritance and ideological appropriations

In the Anglo-American tradition, intergenerational concerns were articulated in differing ways by Thomas Jefferson and Abraham Lincoln. Jefferson wrote that ‘the earth belongs in usufruct to the living: that the dead have neither powers nor rights over it’, employing a civil-law concept to argue that each generation enjoys a temporary, non-absolute interest in the resources it inherits.Footnote ²⁶ The idea of usufruct, use without destructive depletion, reinforced Jefferson’s view that no generation may irrevocably bind its successors through excessive consumption or accumulated debt.

Lincoln, writing in a different political moment, drew more explicitly on Burkean themes of inherited constitutional responsibility.Footnote ²⁷ In the Lyceum Address he described Americans as ‘legal inheritors’ of institutions constructed by earlier generations and emphasised that the task of the living was ‘to transmit these … unprofaned … to the latest generation’.Footnote ²⁸ Read together, Jefferson and Lincoln illustrate two enduring strands of Anglo-American thought on intergenerational obligation: one grounded in limiting the power of the past over the present while recognising each generation’s usufructuary position; the other in preserving institutional goods for the future as part of an inherited legal and political order.

After the Second World War, neoliberalism reframed intergenerational responsibility in terms consistent with its emphasis on individual freedom, limited government and market ordering. Political leaders associated with this tradition frequently invoked obligations to future generations as a justificatory vocabulary for policy choices. Ronald Reagan told the United Nations (UN) in 1982 that failing to uphold ‘simple justice’ would incur ‘the bitter wrath of generations yet unborn’.Footnote ²⁹ Margaret Thatcher argued in 1988 that ‘we do not hold a freehold on our world, but only a full repairing lease’, and that this imposed a duty to transmit it ‘in good order to future generations’.Footnote ³⁰ They helped to normalise the language of ‘future generations’ in public discourse and paved the way for its appearance in soft law instruments, human rights rhetoric and climate negotiations.

2.5. Synthesis: from intellectual motifs to legal architecture

These historical materials reveal three recurring motifs. First, from Genesis through Aquinas and Burke to Jefferson and Thatcher, a persistent idea of stewardship or usufruct: holders of power or property may enjoy its benefits but ought not to destroy the underlying corpus on which successors will depend. Second, from the Roman res communes and Lincoln’s ‘legal inheritors’, certain goods such as territory, institutions and common resources are held under a transgenerational obligation to preserve them. Third, Aristotle’s epieikeia, the Roman prodigus rules and Burkean anxieties about ‘waste’ all point towards the role of equity and equitable-like ideas as correctives to formal entitlements when their exercise would unjustly prejudice others, including those not yet born.

Together, these intellectual strands furnish the conceptual vocabulary that modern jurists use when they speak of the Earth as a ‘trust’ for future generations, of States as ‘trustees’ of natural resources or of present generations holding the planet ‘in usufruct’. As subsequent sections of this article argue, these motifs have been channelled along two main doctrinal pathways: public trust models that treat the State as a fiduciary over shared resources, and equitable models, most notably the constructive trust, that focus on unjust enrichment and unconscionable retention of benefits. The historical evolution explains why contemporary debates about intergenerational equity so readily gravitate towards trust, equity and stewardship, and prepares the ground for evaluating which of those legal architectures is best equipped to convert inherited moral intuitions into enforceable obligations across generations.

3.1. Rawls: distributive justice ‘between generations’

Rawls addresses intergenerational obligations within the architecture of distributive justice. He argues that principles of justice must operate not only among contemporaries but ‘between generations’, requiring each generation to preserve the conditions necessary for just institutions to endure.Footnote ³³ In A Theory of Justice, he maintains that ‘each generation must not only preserve the gains of culture and civilisation, and maintain intact those just institutions that have been established, but it must also put aside in each period of time a suitable amount of capital accumulation’.Footnote ³⁴ He acknowledges that determining the precise extent of this duty ‘seems to admit of no definite answer’, reflecting the difficulty of allocating burdens between temporally dispersed groups who cannot negotiate directly.

Because Rawls’s intergenerational savings principle is framed primarily in terms of capital accumulation, it offers limited guidance for addressing environmental degradation or ecological limits, which were not central to his distributive model.Footnote ³⁵ Its significance for present purposes is therefore not doctrinal but normative: Rawls provides an influential account of why justice must extend beyond relations among contemporaries. Caney’s analysis develops that intergenerational premise in the climate context, arguing that once climate change and related environmental harms are understood as threats to basic interests, there is no principled reason to apply weaker standards of justice simply because the primary victims will be temporally distant rather than contemporaneous.Footnote ³⁶

3.2. Weiss: planetary trust and fiduciary structure

Writing in the context of international environmental law, Weiss develops a legal framework for intergenerational equity. She reconceptualises intergenerational justice in terms of a ‘planetary trust’, positioning each generation as trustee of natural and cultural resources for the benefit of future generations.Footnote ³⁷ According to Weiss, ‘each generation receives a natural and cultural legacy in trust from previous generations and holds it in trust for future generations’, and this relationship entails ‘a duty to act for the benefit of beneficiaries with respect to trust matters’.Footnote ³⁸ Her account translates Rawls’ concern with preserving ‘culture and civilization’ into the language of trusteeship, with clearly identified roles (trustee and beneficiary) and a conceptual trust res encompassing natural and cultural heritage.

On this account, the planetary trust framework is ‘deeply rooted in human behavior and in the cultural norms of communities’, on the basis that private-law doctrines such as wills and family trusts already familiarise legal systems with intergenerational responsibility.Footnote ³⁹ She argues that the leap from intra-familial arrangements to a planetary trust is one of scale rather than of principle: the same fiduciary logic that governs the administration of a family estate can inform the stewardship of the Earth’s resources for future generations.

In her positive law analysis, Weiss identifies the public trust doctrine as the closest existing analogue. Public trusteeship over certain natural resources can be extended conceptually, though not yet doctrinally, into a broader planetary model of fiduciary obligation. In the United States (US), she argues that state and local governments may advance such duties through the exercise of police powers ‘to protect the health and welfare of their citizens’.Footnote ⁴⁰ While the planetary trust remains a normative proposal rather than a settled legal doctrine, Weiss’ work provides a structured legal vocabulary for articulating duties owed to future generations, grounded explicitly in the doctrines and analogies of equity. This vocabulary has in turn influenced public trust and atmospheric trust litigation, where claimants cast States as trustees of environmental resources for present and future beneficiaries.

3.3. Sohn: equity, universality and scepticism about trust analogies

Louis B Sohn offers a contrasting assessment of the feasibility of Weiss’ proposal at the international level. He argues that a doctrine of intergenerational equity cannot rest on the Anglo-American concept of equity or on fiduciary relationships derived from domestic trusts law.Footnote ⁴¹ Instead, he proposes that ‘equity’ in the international context must be understood broadly, closer to a general notion of ‘justice as fairness’ than to a technical body of doctrines.Footnote ⁴² His concern is that equity lacks a uniform meaning across legal traditions, making it an unstable foundation for a universal legal principle. Sohn observes that ‘equity under Anglo-American law means one thing, equity under continental law derived from Roman principles means something different … [t]he same is true for equitable principles under Islamic law, Hindu law, Chinese law, and so on’.Footnote ⁴³

For Sohn, the diversity of legal traditions underscores the difficulty of grounding intergenerational obligations in fiduciary analogies that do not command universal acceptance. He notes that international environmental instruments, such as the Stockholm Declaration on the Human Environment, tend to adopt general aspirational language concerning responsibility to future generations, rather than more specific formulations resembling trust-based obligations.Footnote ⁴⁴

A conceptual tension therefore emerges between the approaches advanced by Weiss and Sohn. Weiss’ model relies on fiduciary analogies drawn from Anglo-American trusts law and presupposes that these concepts can be generalised to the international plane. Sohn, by contrast, argues that the diversity of equitable traditions across legal systems precludes grounding a universal principle of intergenerational equity in the vocabulary of fiduciary obligation. On his account, equity must refer to a broad ideal of fairness rather than to technical doctrines associated with trusts. This divergence has significant implications: while Weiss’ framework offers a structured legal analogy capable of generating determinate duties, Sohn’s conception operates at a higher level of abstraction and does not, in itself, establish fiduciary responsibilities enforceable in positive law.

3.4. Trust analogies in practice: international trusteeship and beyond

Sohn’s scepticism regarding the transplantation of Anglo-American trust doctrines into international law has prompted counterarguments pointing to existing trust-like structures within the international legal system. John Head observes that the UN International Trusteeship System, established in 1945, ‘reflected the main contours of an equitable trust’, even though it did not adopt the terminology or doctrinal features of domestic trusts law.Footnote ⁴⁵ He notes that international institutional arrangements ‘bearing the marks of a trust, whether carrying that label or not, have been developed for various other purposes as well, including for environmental protection’.Footnote ⁴⁶

Later sections of this article argue that a shift in focus is warranted: rather than seeking to universalise the public trust or to construct a planetary trust at the international level, it may be more productive to identify doctrinal vehicles within domestic legal systems that can operationalise intergenerational equity in a way that is legally orthodox and remedially effective. The constructive trust, grounded in unjust enrichment and equitable conscience, and already embedded across common law and mixed jurisdictions, offers one such vehicle. While it shares with Weiss’ planetary trust a concern for fiduciary-like responsibilities across time, it is anchored in established doctrine and does not depend on importing the full apparatus of Anglo-American trusts law into international law.

4.1. International declarations and treaty instruments

A useful starting point is Principle 1 of the Stockholm Declaration on the Human Environment.Footnote ⁴⁷ Principle 1 affirms a right to conditions of life in an environment compatible with dignity and well-being, coupled with a ‘responsibility’ to protect and improve the environment for present and future generations.Footnote ⁴⁸ The Report of the World Commission on Environment and Development (Brundtland Report) entrenched intergenerational concerns within the discourse of ‘sustainable development’, defining the concept as ‘development that meets the needs of the present without compromising the ability of future generations to meet their own needs’.Footnote ⁴⁹ Subsequently, the Rio Declaration on Environment and Development embedded intergenerational language in soft law.Footnote ⁵⁰ Principle 3 states that ‘the right to development must be fulfilled so as to equitably meet developmental and environmental needs of present and future generations’.Footnote ⁵¹

Article 3(1) of the UN Framework Convention on Climate Change (UNFCCC) provides that States Parties ‘should protect the climate system for the benefit of present and future generations of humankind, on the basis of equity and in accordance with their common but differentiated responsibilities and respective capabilities’.Footnote ⁵² The Paris Agreement follows this pattern.Footnote ⁵³ Its preamble states that States Parties ‘should, when taking action to address climate change, respect, promote and consider their respective obligations on human rights … as well as intergenerational equity’.Footnote ⁵⁴ Intergenerational equity is repeatedly affirmed as an ideal, but remains preambular, principled and non-self-executing.

4.2. Judicial and quasi-judicial engagement with intergenerational harm

Within adjudication, intergenerational arguments appear in the following bodies of case law:

1. (i) early and foundational decisions recognising standing or ‘responsibility’ to future generations;

2. (ii) international and regional human rights decisions that foreground the temporal dimension of environmental harms;

3. (iii) Global South and domestic constitutional cases explicitly invoking intergenerational equity and, in some instances, public trust language; and

4. (iv) recent climate and public trust litigation in North America and Europe that illustrates both the potential and limits of the public trust as a doctrinal vehicle.

4.3. Reconceptualising the public trust: intellectual proposals and their limits

Mary Christina Wood’s ‘Nature’s Trust’ framework proposes that governments hold the natural environment, including the atmosphere, in trust for present and future generations and that this fiduciary status ‘breathes legal right’ into intergenerational equity.Footnote ⁸⁹ Wood argues that trust principles provide determinate fiduciary standards (prudence, loyalty, impartiality) that can be judicially enforced against States that fail to protect ecological integrity for future beneficiaries. Atmospheric trust theorists extend this logic to the global commons, suggesting that States hold the atmosphere in a form of joint trust and must allocate a ‘carbon budget’ consistently with intergenerational equity.Footnote ⁹⁰

Edith Brown Weiss’ ‘planetary trust’ model likewise draws on Anglo-American trust concepts, positing that each generation acts as trustee of the Earth’s natural and cultural heritage for both current and future generations.Footnote ⁹¹ She identifies three core principles, namely conservation of options, quality and access, which are intended to structure intergenerational obligations. Although formulated within international law and policy, Weiss’ approach presupposes that trust duties can be generalised beyond domestic equity, with ‘mankind’ as both beneficiary and, in some formulations, co-trustee.

Caroline Cress and other atmospheric trust critics question whether it is institutionally appropriate for courts, rather than legislatures and specialist agencies, to manage complex climate policy via expansive fiduciary standards. Cress notes that placing ‘all management decisions affecting the atmosphere’ in the hands of generalist judges with limited scientific expertise risks displacing democratic accountability and technocratic competence.Footnote ⁹²

Moreover, a difficulty, visible in both Wood’s and Weiss’ models, is their reliance on the terminology of ‘trust’ that elides the structural requirements of trusts in Anglo-equitable doctrine. Comparative public trust scholarship, particularly James Huffman’s, emphasises that ambitious accounts of the doctrine often rest on a mythologised history linking it to Roman law and the Magna Carta, whereas in practice it has supported only limited and carefully defined public rights, in relation to navigation and fishing.Footnote ⁹³ As James Huffman and others point out, a legal trust in this tradition requires a settlor, trustee, beneficiary, trust res and separation of legal and equitable title. Treating ‘the people’, or humanity at large, as simultaneously settlor, trustee and beneficiary stretches these categories beyond recognition. Neither model resolves the question of how future generations, who lack legal personality, can function as beneficiaries with enforceable rights, a problem mirrored in Neubauer and constitutional decisions.

The upshot is that while these projects succeed in foregrounding intergenerational equity and have influenced litigation strategies (for example, in Juliana, or atmospheric trust suits in US state courts), they do not furnish a doctrinal path for courts operating within strict common-law or civil-law frameworks. Their reliance on a metaphorical notion of ‘trust’ runs against both orthodox trusts law and the judicial reluctance, documented previously, to constitutionalise fiduciary duties owed to undefined publics and future persons.

4.4. Doctrinal limits of the public trust doctrine

Four limits are especially salient. First, in many jurisdictions the public trust doctrine simply does not exist as a justiciable doctrine capable of imposing fiduciary-type duties on the State. La Rose is explicit: recognising a public trust over air, water and permafrost would require the federal Crown to exercise continuous supervision and control over vast resources. The Court emphasised the limited circumstances in which trust-like duties may be imposed on the Crown and rejected the existence of a general public trust doctrine in Canadian law.Footnote ⁹⁴ Similar reluctance appears, if less starkly, in other common law jurisdictions that have resisted transplanting US-style public trust doctrine into their constitutional orders, reflecting wider scholarly scepticism about ambitious attempts to universalise the doctrine beyond its historically contingent US roots.Footnote ⁹⁵

Second, where public trust obligations are constitutionally entrenched, courts have been cautious in the remedies that they order. In Held, the Court relied on explicit constitutional text requiring the State and ‘each person’ to maintain a clean and healthful environment ‘for present and future generations’ and acknowledged an intergenerational trust.Footnote ⁹⁶ Yet, the remedy was declaratory: the impugned statutory provisions were invalidated, but no fiduciary accounting, proprietary relief or ongoing supervisory mechanism akin to trust administration was imposed.

Third, constitutional courts have declined to recognise future generations as rights-bearing beneficiaries. Neubauer is paradigmatic: the German Federal Constitutional Court accepted an objective duty of intergenerational protection under the Basic Law but insisted that future generations ‘do not yet carry any fundamental rights’.Footnote ⁹⁷ Intergenerational obligations operate on the objective level of State duties, while subjective rights remain confined to existing persons. This asymmetry means that even where public trust or intergenerational language appears in constitutional text, future generations cannot themselves be beneficiaries in the sense required by trusts law; their interests must instead be mediated through present-rights claims.

Fourth, the public trust doctrine as deployed in environmental contexts does not satisfy the structural requirements of a trust in Anglo-equitable doctrine. As Huffman observes, trusts law presupposes a division between legal and equitable title: one person (or set of persons) cannot simultaneously be settlor, trustee and sole beneficiary.Footnote ⁹⁸ In public trust formulations, however, ‘the public’ or ‘the people’ often occupy all three positions: they are said to establish the trust, act through the State as trustee and also be its beneficiaries. The State itself frequently enjoys the primary benefit of resource exploitation (through revenues, development, political support), further complicating any separation between legal and beneficial interests.

The cases surveyed in Section 4.2 show that courts are increasingly prepared to acknowledge that environmental harms unfold over time and that present actions constrain future options. They are less willing, however, to superimpose a fully-fledged trust framework on these temporal dynamics. Public trust arguments tend to succeed only where constitutional text already entrenches something akin to a trust (as in Montana or Hawai’i), and even then the resulting obligations are filtered through familiar public-law mechanisms.Footnote ⁹⁹ Where such text is absent, as in La Rose, courts resist importing a public trust from US jurisprudence; and where plaintiffs seek to rely on public trust to ground systemic climate remedies, as in Juliana, separation-of-powers concerns prove decisive.Footnote ¹⁰⁰

Significantly, the public trust lacks: (i) consistent recognition across jurisdictions; (ii) a clear class of beneficiaries with legal personality; (iii) the dual-title structure required for proprietary remedies; and (iv) an accepted basis for judicially managing long-term resource policy without running afoul of democratic theory objections. This doctrinal fragility also bears out, from a different angle, broader concerns that existing human rights frameworks lack an adequate ‘constitutional architecture’ for intergenerational justice.Footnote ¹⁰¹ The argument advanced in this article can be read as one such design proposal at the domestic level: it suggests that constructive trust reasoning can supply part of the missing legal architecture by translating intergenerational human rights concerns into enforceable obligations attached to specific assets.

The next section argues that the constructive trust, properly understood, avoids several of these structural shortcomings. Because it arises by operation of law in response to unjust enrichment or unconscionable retention of benefits, it does not depend on constitutional entrenchment or prior legislative recognition. Its doctrinal foundation in equity, its capacity to attach proprietary consequences to wrongful gains and its recognised flexibility across common law and mixed systems make it a more promising framework for converting intergenerational environmental inequities into legally cognisable obligations attached to specific assets.

5.1. The constructive trust: doctrinal profile and conceptual foundations

The constructive trust emerged in early English Chancery as a response to situations in which legal title was acquired or retained in circumstances that equity regarded as unconscionable. While the doctrine developed within private law, that origin is not disabling for present purposes. Human rights law increasingly addresses hybrid formations of power in which States, State-owned enterprises and inadequately regulated private actors participate in the production and retention of benefits derived from rights-impairing conduct. In such situations, constructive trust reasoning can serve as a remedial model to prevent unjustified benefits from hardening into a legally protected advantage. Modern restitution and equity scholars have emphasised this ‘unconscionable retention’ function as the core of the institution, whether expressed in the language of unjust enrichment (Burrows) or in broader, conscience-based terms (Millett, Virgo).Footnote ¹⁰²

In Keech v Sandford,Footnote ¹⁰³ the Lord Chancellor held that the renewed lease was held on trust for the beneficiary and insisted that the rule be ‘strictly pursued, and not in the least relaxed’.Footnote ¹⁰⁴ From this decision flows the strict fiduciary no-profit rule: a fiduciary must not obtain and retain any unauthorised benefit by reason of the fiduciary position, regardless of good faith. Functionally, this is a rule that prevents those in structurally privileged positions from converting entrusted power into private advantages, a theme that resonates with human rights constraints on State and corporate abuses of authority.

Modern courts have reaffirmed and generalised this principle. In Boardman v Phipps Footnote ¹⁰⁵ and FHR European Ventures LLP v Cedar Capital Partners LLC,Footnote ¹⁰⁶ the House of Lords and the United Kingdom Supreme Court confirmed that a fiduciary who receives a profit in breach of duty holds it on constructive trust for the principal and that the principal acquires a proprietary interest in that benefit. In Attorney-General for Hong Kong v Reid,Footnote ¹⁰⁷ the Privy Council extended this reasoning to bribes, treating them as held on constructive trust for the State. These authorities locate the constructive trust at the core of fiduciary accountability: it is the mechanism by which equity strips ill-gotten gains from persons occupying structurally advantaged positions and reroutes those gains to the persons or entities whose interests should have been protected, a logic directly analogous to gain-based remedies for serious human rights abuses.

Although the constructive trust developed in fiduciary contexts, its reach is broader. In Westdeutsche Landesbank Girozentrale v Islington LBC,Footnote ¹⁰⁸ Lord Browne-Wilkinson described a constructive trust as arising by operation of law whenever it would be unconscionable for the holder of legal title to deny another’s beneficial interest. In Paragon Finance plc v D B Thakerar & Co,Footnote ¹⁰⁹ Millett LJ similarly stated that a constructive trust arises whenever it would be unconscionable for an owner to assert full beneficial ownership and deny another’s interest. Canadian jurisprudence has taken a particularly explicit approach. In Soulos v Korkontzilas,Footnote ¹¹⁰ McLachlin J characterised the constructive trust as ‘an ancient and eclectic institution’ of equity, imposed by law not only to address unjust enrichment but more generally to hold persons to high standards of trust and probity and to prevent them from retaining property which, in good conscience, they should not be permitted to retain. On her account, constructive trusts may be imposed even in the absence of material loss or classical unjust enrichment where conscience so requires. Unlike the public trust’s often mythic pedigree discussed in Section 4, this ‘ancient’ status is grounded in a continuous line of equitable practice and case law, rather than in a reconstructed constitutional narrative.Footnote ¹¹¹

On the remedial side, the common law distinguishes between institutional and remedial constructive trusts. The distinction has generated a substantial theoretical literature: some writers insist that all constructive trusts are ‘institutional’ in nature and merely recognised by the court, whereas others defend an expressly remedial, discretionary model in which the court may shape proprietary responses ex post to do justice in novel situations (notably McLachlin J in Soulos and academic accounts by McInnes and Tey).Footnote ¹¹² The Canadian Supreme Court has recognised both models, while English law is more cautious about expressly remedial trusts but accepts institutional constructive trusts across a range of situations. In both traditions, however, the crucial point is that constructive trusts carry proprietary consequences: they create equitable interests in specific assets, permit tracing into substitutes and can support powerful remedies, such as accounts of profits and disgorgement.

In many common law jurisdictions, constructive trusts also operate within unjust enrichment frameworks. Canadian law, for example, treats the constructive trust as a possible remedy where a claimant establishes enrichment, corresponding deprivation and absence of juristic reason, in a way that tracks the influential ‘unjust factors’ analysis associated with Burrows while preserving equity’s concern with conscience.Footnote ¹¹³ By ‘juristic reason’, Canadian restitution law refers to a recognised legal basis that justifies the defendant’s retention of the benefit, such as a valid contract, a gift or a statutory obligation. Thus, if A pays money to B, pursuant to a binding contract, B’s enrichment is supported by a juristic reason, being the binding contract, and restitution will not be available. By contrast, where no such legal basis exists, the enrichment may be treated as unjust. In such cases, the trust is not grounded in fiduciary status but in the inequity of allowing a defendant to retain a benefit without legal justification. This unjust enrichment branch sits alongside, rather than replacing, the conscience-based and fiduciary branches. When coupled with human rights obligations such as duties to prevent serious environmental degradation that threatens rights to life, health or private life, this structure offers a way to conceptualise the profits associated with rights-violating conduct as unjust gains to which equity can attach and redirect.

Moreover, the constructive trust is not an exotic or marginal device; it is an orthodox, general-purpose instrument by which equity responds to structurally problematic gains. Its organising criterion is not historical status (for example, whether something has traditionally been labelled a ‘public trust’) but equitable conscience: whether, in light of identifiable benefits and burdens, it is consistent with good conscience to allow a person or class to retain the benefit free from obligations to others. Doctrinal syntheses by Virgo, likewise, depict the constructive trust as equity’s principal means of converting abstract notions of ‘conscience’ into concrete proprietary consequences. That characterisation dovetails with its proposed role in an intergenerational human rights context.Footnote ¹¹⁴

These features make the constructive trust a plausible candidate for addressing intergenerational harm in a human rights framework, where present actors benefit from resource exploitation while shifting costs onto future persons whose rights to life, health, an adequate environment or cultural integrity will be burdened.

5.2. Jurisprudential functions relevant to intergenerational equity

Rather than cataloguing cases serially, this section groups constructive trust jurisprudence by function, highlighting those aspects most relevant to intergenerational human rights claims: strict fiduciary accountability, unjust enrichment and gain-based remedies, conscience-based intervention in the absence of classic fiduciary relationships and proprietary consequences.

The first relevant function is strict fiduciary accountability. Keech, Boardman, FHR and Reid collectively establish that a fiduciary who makes unauthorised profits by virtue of fiduciary status must hold them on constructive trust for the beneficiary, even if no loss can be shown and even if the fiduciary acted honestly.Footnote ¹¹⁵ Courts have not shied away from imposing constructive trusts over significant assets in order to enforce this rule. The point is structural: persons in positions of entrusted power may not convert opportunities arising from that position into personal gains. For human rights law, this function is analogous to the remedial principle that public authorities and private actors exercising public functions should not be left with the benefit of conduct that infringes fundamental rights, and that restitutionary or disgorgement-style relief may form part of an effective remedial response where ordinary compensation is inadequate.Footnote ¹¹⁶

A second function concerns unjust enrichment and gain-based remedies. In Garland v Consumers’ Gas Co Footnote ¹¹⁷ and Kerr v Baranow,Footnote ¹¹⁸ the Supreme Court of Canada confirmed that constructive trusts may be awarded to remedy unjust enrichment where monetary restitution is inadequate, provided there is a sufficient link between the enrichment and a specific asset. The constructive trust in such cases operates as a proprietary response to the unjust enrichment, not as a recognition of pre-existing fiduciary status. This shows that constructive trusts are not confined to classic fiduciary settings; they can be deployed whenever enrichment, deprivation and lack of juristic reason intersect with property. In the human rights context, this is directly relevant for situations in which unlawful environmental degradation found to violate rights to life, health, private life or indigenous cultural rights has generated identifiable profit streams. The same logic that justifies proprietary remedies in private unjust enrichment cases can justify requiring that those profit streams be held and applied in ways that vindicate the rights that were violated, including through measures benefiting future generations. Restitution scholars have long argued that disgorgement and proprietary restitution are justified where wrongful gains would otherwise escape ordinary compensatory logic; constructive trusts provide one principal vehicle through which that logic is implemented by conferring an equitable proprietary interest in specific assets or their traceable proceeds.Footnote ¹¹⁹

A third function is conscience-based intervention beyond formal fiduciary labels. Soulos is the leading statement. McLachlin J accepted that constructive trusts may be imposed even without unjust enrichment in the strict sense, where property has been obtained in circumstances such that it would be against good conscience for the defendant to retain it. She emphasised that the category of relationships in which such obligations arise is not closed and that the constructive trust can serve prophylactic, deterrent and institutional functions in holding persons to high standards of honesty and good faith. Earlier English authority such as Hussey v Palmer Footnote ¹²⁰ similarly described the constructive trust as a trust imposed whenever justice and good conscience require it, though English law has since moved towards a somewhat more structured conception. This conscience-based branch aligns with human rights courts’ increasing reliance on ‘systemic’ or ‘structural’ remedies in cases involving recurrent violations; it also reflects equity’s role in policing ‘bad faith’ exercises of legal power even in the absence of a pre-existing fiduciary label.Footnote ¹²¹

A fourth function concerns proprietary consequences and their systemic significance. Cases such as Reid demonstrate that constructive trusts can have dramatic effects, effectively confiscating assets that would otherwise form part of a wrongdoer’s estate and reallocating them to the person in whose favour equity intervenes.Footnote ¹²² Academic commentary on such cases has emphasised that constructive trusts can recharacterise the ownership of gains arising from wrongdoing, subordinating competing claims of creditors or third parties where necessary. This confirms that constructive trusts are not merely symbolic declarations of fault; they are capable of redirecting wealth flows in ways that respond to the normative judgment that certain benefits cannot, in good conscience, be retained absolutely. For human rights purposes, this capacity is crucial in contexts where violations are profitable and where ordinary compensatory damages risk leaving the underlying incentive structure intact.

Finally, the distinction between institutional and remedial constructive trusts illustrates the doctrine’s adaptability. In Westdeutsche and subsequent English cases, institutional constructive trusts arise automatically once specified conditions are met, such as the receipt of property in breach of trust. In Canadian and some other common law authorities (for example, Soulos and Pettkus v Becker), remedial constructive trusts may be crafted in novel situations, subject to principled constraints, where equitable conscience requires a proprietary response.Footnote ¹²³ Both models are relevant for intergenerational equity within a human rights framework: institutional logic allows automatic attachment of trusts to gains at the moment they are realised through rights-infringing conduct, while remedial logic allows courts to design trust remedies ex post in light of systemic patterns of enrichment and harm that have been judicially recognised as violating environmental or related human rights. Taken together, this jurisprudence shows that constructive trusts are routinely used to address structural asymmetries of power and benefit.

5.3. Constructive trusts and intergenerational equity: doctrinal fit and advantages over public trusts

The intergenerational problem is structurally familiar from a human rights perspective: present actors (States, corporations and current populations) obtain significant benefits from the exploitation of finite environmental resources and from activities that emit greenhouse gases, while a substantial portion of the costs will be borne by future persons who have no voice in present decision-making but whose rights to life, health, private and family life, culture and a viable environment are foreseeably threatened. As Caney emphasises, however, these intergenerational patterns are layered onto existing intragenerational inequalities: the present-day beneficiaries of carbon-intensive activity are not coextensive with those who will bear the heaviest burdens, either now or in the future.Footnote ¹²⁴ Any plausible account of intergenerational equity must therefore confront not only the temporal distribution of harm, but also the way in which present gains are concentrated among particular States, classes and corporate actors. The constructive trust model proposed here reflects that dual structure by targeting identifiable profit streams associated with rights-violating conduct, rather than treating ‘humanity as a whole’ as both undifferentiated wrongdoer and victim. Yet, existing human rights practice has not generally taken that step. Human rights bodies have instead tended to rely on positive obligations and proportionality analysis, leaving the remedial implications for unjust gains underdeveloped.Footnote ¹²⁵

By contrast, the constructive trust does not depend on an a priori characterisation of the State as ‘trustee of the public’. It responds instead to the circumstances of enrichment and harm once a human rights violation has been established. This remedial, enrichment-centred orientation picks up the line of analysis developed in the constructive trust literature that treats the institution as a response to wrongful gains and structural opportunism (for example, the theories of ‘wrong-based’ constructive trusts advanced by Chambers and Virgo), rather than as an exhaustive taxonomy of fixed ‘categories’.Footnote ¹²⁶ The doctrinal question is whether present actors have obtained and retained identifiable benefits in circumstances where it would be unconscionable, in light of the rights at issue, to treat those benefits as fully their own, free from obligations to those who will bear the costs.

At the level of unjust enrichment, the basic elements are familiar: (1) an enrichment; (2) a corresponding deprivation; and (3) absence of a juristic reason. One can plausibly argue that certain gains realised from activities that significantly degrade a shared environmental resource constitute an enrichment to the present generation and to specific State or private actors, accompanied by a corresponding deprivation for those who will inherit a diminished environment and whose human rights will thereby be impaired. Once that frame is accepted, a constructive trust can, in principle, be imposed over the gains in question, requiring that they be held not absolutely but subject to obligations to restore, remediate or otherwise protect environmental interests that will matter for future rights-holders.

The conscience-based branch of constructive trust doctrine is equally, and perhaps more, apt. Soulos confirms that constructive trusts may be imposed to uphold high standards of probity where property has been acquired in circumstances that engage equitable conscience, even in the absence of strict unjust enrichment.Footnote ¹²⁷ Systemic patterns of environmental exploitation, where actors knowingly pursue profit in ways that foreseeably and gravely compromise the conditions of life for future generations, are at least analogous in moral structure to fiduciaries exploiting their positions for personal gain. The wrongdoing lies not in a breach of an express fiduciary undertaking, but in taking advantage of a structural asymmetry: the incapacity of future persons to bargain or protect their own interests against current decision-makers, coupled with the breach of present human rights obligations to avoid exposing individuals to serious environmental risks. In such circumstances, equity’s insistence that no one may retain benefits in ‘bad conscience’ provides a doctrinal foothold for intergenerational constructive trusts that are triggered by, and responsive to, judicial findings of human rights violations. This, in turn, yields a set of concrete advantages over the public trust.

First, constructive trusts do not require constitutional amendment or explicit statutory creation. They arise by operation of law within existing equitable frameworks once a relevant wrong has been found.Footnote ¹²⁸ This is crucial in jurisdictions where courts have rejected efforts to constitutionalise the public trust or have held that a public trust doctrine ‘does not exist’ in domestic law. A constructive trust claim can be framed in terms of recognised equitable categories of unjust enrichment, wrongful gain or unconscionable retention arising out of an established human rights breach, without inviting courts to import a historically controversial doctrine from another legal system.

Second, constructive trusts do not depend on recognising future generations as immediate rights-holders in the constitutional sense. Courts, as in Neubauer, have tended to deny fundamental-rights status to unborn persons, but this does not preclude representative proceedings on behalf of future interests or the use of present claimants as conduits for intergenerational arguments.Footnote ¹²⁹ In constructive trust terms, the present generation’s enrichment at the expense of future persons can be addressed by treating certain assets or revenues as impressed with equitable obligations, even if the ultimate beneficiaries are represented through present plaintiffs, guardians ad litem, public institutions or human rights bodies.

Third, constructive trusts offer a richer remedial toolkit for human rights adjudication. Public trust litigation has, so far, predominantly yielded declaratory and injunctive relief, with limited or no proprietary consequences.Footnote ¹³⁰ Constructive trusts, by contrast, can support proprietary claims to specific assets or revenue streams, tracing into substitutes and accounts of profits.Footnote ¹³¹ In intergenerational settings, this would allow courts or human rights bodies to earmark parts of the gains derived from environmentally-harmful activities for the benefit of future persons, whether through dedicated remediation funds, long-term conservation trusts, climate-adaptation funds or other institutional arrangements that satisfy the human rights requirement of effective reparation.

Fourth, constructive trusts are more manageable from the perspective of democratic theory than sweeping public trust models. Public trust critics worry that a broad fiduciary duty to the public allows courts to supervise policy choices in a way that sidelines legislatures and agencies.Footnote ¹³² Constructive trust reasoning, as proposed here, is narrower: it targets specific gains that equity deems improperly retained and imposes obligations only in respect of those gains, and only after a human rights breach has been established by reference to existing constitutional or treaty-based standards. Courts remain within their traditional role of regulating unjust enrichment and wrongful gain and of fashioning effective remedies for rights violations, rather than assuming global managerial control over environmental policy. None of this suggests that courts have already recognised an intergenerational constructive trust. They have not done so.

5.4. Transferability: constructive trust logic beyond the common law

The trans-systemic plausibility of constructive trust reasoning is reinforced by the long-standing framing of intergenerational obligation in terms of usufruct. As Section 2 showed, both civil-law doctrine and Anglo-American political thought have understood generational authority over resources as a form of limited enjoyment: present holders may use and take the fruits of a patrimony, but they ought not to impair its substance for successors. Jefferson’s characterisation of the earth as held by the living only in a usufructuary capacity crystallises this intuition in expressly temporal terms and links it to questions of debt, waste and institutional continuity.Footnote ¹³³ Civil-law concepts of usufruct and patrimonial segregation thus already provide a language in which intergenerational obligations are conceived as constraints on present enjoyment for the sake of future beneficiaries. This vocabulary offers a natural bridge for translating constructive trust logic into civil-law settings without requiring reception of ‘trust’ as a technical category.

Although the constructive trust is a common law device, its underlying logic is mirrored in other legal traditions, particularly where constitutional or treaty-based environmental rights have been recognised. This increases its appeal as a model for intergenerational equity in a global doctrinal landscape, especially when contrasted with the public trust’s uneven reception. Civil-law systems typically do not use trust terminology, but they recognise unjust (or unjustified) enrichment as a general principle. German law provides a suite of ‘condictiones’ under the law of unjustified enrichment; French law, following the 2016 reform, codifies ‘l’enrichissement injustifié’ as a residual basis of restitution.Footnote ¹³⁴ These regimes embody the same normative intuition that underpins constructive trusts in unjust enrichment contexts: no one should retain a benefit at another’s expense without a recognised legal cause. Similarly, doctrines of abuse of rights, good faith and limits on ownership (such as obligations to respect neighbours, the environment or public order) operate to constrain the otherwise absolute exercise of property rights in ways that resonate with equity’s concern for conscience and with human rights limitations on disproportionate interferences with protected interests.

The Québec ‘fiducie’ and ‘patrimoines d’affectation’ allow property to be segregated from a person’s general patrimony and dedicated to a specific purpose or group of beneficiaries.Footnote ¹³⁵ Comparative private-law scholarship has underlined that Québec patrimonies by appropriation and related social-utility trusts are particularly well suited to environmental protection, including as vehicles for the long-term stewardship of natural resources and cultural heritage.Footnote ¹³⁶ Functionally, these institutions perform the same work a constructive trust would perform under common law: they earmark assets and subject them to legal constraints for the benefit of interests that might otherwise be inadequately protected, including intergenerational environmental interests recognised as aspects of rights to a healthy environment or to cultural continuity. Read through the lens of usufruct, they confirm that domestic private law already accommodates temporal limits on ownership and the idea that present enjoyment must be structured with regard to future claimants.

Constitutional environmental rights provisions provide a further point of convergence. Section 24 of the Constitution of the Republic of South Africa guarantees everyone the right to an environment not harmful to health or well-being and requires measures to secure sustainable development ‘for the benefit of present and future generations’.Footnote ¹³⁷ Several Latin American legal orders have moved towards recognising nature as a subject of rights. Ecuador’s Constitution explicitly grants rights to nature, Bolivia’s Constitution and subsequent Law of the Rights of Mother Earth develop a related model and Colombian courts have recognised the rights of nature through constitutional jurisprudence.Footnote ¹³⁸ Courts in these systems already treat the temporal distribution of environmental harm and benefit as legally relevant and are willing to order structural remedies, often via ‘amparo’ or ‘tutela’ proceedings, without invoking public trust language.Footnote ¹³⁹ The constructive trust model can map onto these contexts as a way of structuring proprietary and gain-based remedies when environmental-rights violations have generated identifiable profit streams, while the underlying idea of usufruct, understood as use without destructive depletion, provides a familiar conceptual framework for limiting present gains in light of future interests.

In this landscape, the public trust doctrine is comparatively parochial. It originates in US case law concerning the ownership by individual states of navigable waters and submerged lands and has travelled only unevenly.Footnote ¹⁴⁰ Outside a small group of common law jurisdictions, courts and legislatures have tended to constitutionalise environmental rights directly, or to rely on administrative and planning law, rather than importing a US-style public trust with private-law fiduciary incidents. The resistance documented in La Rose, in which the Court declined to recognise any general public trust over environmental resources, sits comfortably with this broader pattern.Footnote ¹⁴¹

Constructive trust reasoning, by contrast, can in principle be translated into these systems without insisting on the adoption of the constructive trust as a named category. A civil law court could treat profits from ecologically destructive activities as unjustified enrichment vis-à-vis current and future rights-holders under a constitutional right to a healthy environment and order that a defined portion of those gains be placed in a segregated patrimony or fund dedicated to remediation and protection, drawing on existing enrichment actions, patrimonial-segregation techniques and the established limits on usufructuary powers. A constitutional court in a system that recognises a right to an ecologically balanced environment ‘for present and future generations’ could characterise severe environmental depletion as a form of unconscionable benefit-retention by present actors and justify proprietary or quasi-proprietary remedies that, in function if not in name, mirror constructive trust relief.Footnote ¹⁴²

The constructive trust is therefore not proposed as a rigid doctrinal transplant but as a model of how law can convert intergenerational inequities, namely present enrichment coupled with future deprivation of human rights-protected interests, into legally cognisable obligations attached to specific assets. Because its underlying logic is already reflected in unjust enrichment regimes, patrimonies of affectation, constitutional environmental rights and long-standing usufructuary understandings of generational authority, it offers a more adaptable and conceptually coherent foundation for intergenerational equity than the historically contingent and jurisdictionally fragile public trust.

5.5. Objections and limits