Article I, section 10, of the US Constitution disallows states from entering into “any Treaty, Alliance, or Confederation,” and it requires that they obtain the “consent of Congress” in order to “enter into any Agreement or Compact with … a foreign Power.”Footnote 1 This language appears to require that, to the extent that US states are ever allowed to conclude agreements with foreign governments, they must obtain congressional approval. This requirement was the subject of litigation during the Trump administration when the national government unsuccessfully sought to challenge a climate change agreement made by the state of California with Québec.Footnote 2 As it turns out, US states often enter into agreements with foreign governments, including sub-national governments, including with Canada and its provinces. Yet states almost never seek congressional approval for these agreements, and the number of these unapproved agreements has been growing substantially in recent years. Notwithstanding the Trump administration’s lawsuit, Congress and the executive branch have generally accepted this development — and, indeed, in some ways, they have encouraged it. There are nevertheless potential flashpoints that could produce federal-state friction in the years ahead.
These sub-national agreements provide an illustration of how the US constitutional law of foreign affairs has evolved over time and is often found more in historical practice than in the text of the Constitution.Footnote 3 The agreements also reveal that, although it is sometimes said that the conduct of foreign affairs is exclusively a national prerogative,Footnote 4 federalism is a vibrant part of the United States’ (and many other nations’) international relations. Finally, the agreements highlight a broader question that deserves greater attention, which is whether it makes sense for requirements and limitations in both domestic law and international law to turn sharply on a distinction between binding and non-binding agreements.Footnote 5 The first section of this article describes the US constitutional law relating to state international agreements. The second section explains that, despite what the text of the Constitution might suggest, states generally do not seek congressional approval for these agreements. The third section recounts the litigation over the California-Québec agreement and the reasons that the court gave for rejecting the Trump administration’s challenges. The fourth section discusses the recent growth in state international agreements and the potential for conflicts with national policy. The fifth section explains how this growing practice relies in part on a sharp distinction between binding and non-binding agreements that merits greater scrutiny than it has yet received.
1. State international agreements
The US Constitution, which took effect more than 230 years ago, is the oldest written constitution in the world. One of the goals of the constitutional founders was to enhance the foreign affairs powers of the national government because there was a perception that the country was not as effective in international affairs as it should be. In the years leading up to the adoption of the Constitution, the country operated under a treaty-like arrangement known as the Articles of Confederation, but this arrangement was widely viewed as being inadequate. As the historian Walter LaFeber observed, “[n]othing contributed more directly to the calling of the 1787 Constitutional Convention than did the spreading belief that under the Articles of Confederation, Congress could not effectively and safely conduct foreign policy.”Footnote 6 In arguing for the adoption of the Constitution, Alexander Hamilton complained that “[w]e may indeed with propriety be said to have reached almost the last stage of national humiliation. There is scarcely any thing that can wound the pride, or degrade the character of an independent nation, which we do not experience.”Footnote 7
Despite the founders’ goal of strengthening the national government, the Constitution preserved a federal structure, in part by giving the national government limited and enumerated power and by reserving the remaining powers to the states and the people, an idea subsequently reflected in the Tenth Amendment to the Constitution.Footnote 8 But there was less support for federalism with respect to the conduct of international affairs. As James Madison contended, “[i]f we are to be one nation in any respect, it clearly ought to be in respect to other nations.”Footnote 9 Even Thomas Jefferson, a defender of states’ rights, reasoned that the United States should be “made one nation in every case concerning foreign concerns.”Footnote 10 In addition to assigning various foreign affairs powers to the national government, the Constitution sought to ensure national control over foreign affairs in two basic ways — through the Supremacy Clause and through express prohibitions on certain state foreign affairs activities.
A. Federal pre-emption
One way in which the Constitution sought to ensure national control over foreign affairs was through the Supremacy Clause, which makes the Constitution, federal laws, and treaties the supreme law of the land, binding on the states.Footnote 11 The Supremacy Clause, when combined with the extensive array of legislative powers assigned to Congress in Article I of the Constitution, gives the national government substantial ability to pre-empt state laws and activities. This pre-emption is generally straightforward when Congress or an international agreement made by the national government expressly provides for pre-emption or where there is a direct conflict between federal and state law. Congress has broad authority to regulate, especially under its commerce power.Footnote 12 And the US Supreme Court has held that the national government’s treaty power is even broader and can address matters that Congress could not otherwise address.Footnote 13
The US Supreme Court has also made clear that pre-emption can occur where the conflict with federal law is indirect. For example, the court has held that a federal statute may evince an intent by Congress to occupy a particular field of regulation (for example, an aspect of immigration enforcement), in which case any state laws in that field are pre-empted.Footnote 14 In addition, the court has held that state laws or actions that stand as an obstacle to the achievement of the policies in a federal statute or agreement may be pre-empted.Footnote 15 Under these doctrines of “field pre-emption” and “obstacle pre-emption,” state laws or actions may be set aside even if it is possible to comply with both federal and state law. Many state activities relating to foreign affairs, it should be noted, do not conflict with federal law, even indirectly. For example, most of the states have offices overseas and send trade and diplomatic representatives to meet with foreign officials, and this interaction is not viewed as being pre-empted. States and municipalities also often take a position on international issues — for example, by issuing non-binding resolutions relating to subjects like arms control and human rights — a form of speech that has not typically been thought to be subject to pre-emption, even though foreign governments sometimes complain to the national government about these expressions.Footnote 16
More controversially, states sometimes limit their investments and contracting with respect to particular countries as a result of foreign events. In theory, these measures can be found to be pre-empted if they conflict with federal sanctions laws. This is what the US Supreme Court concluded in a 2000 decision with respect to a Massachusetts law that restricted purchases from companies doing business with Burma.Footnote 17 But Congress often avoids pre-empting even these types of state measures and sometimes specifically endorses them. In the 1980s, Congress did not include a pre-emption provision in its sanctions legislation against South Africa, despite the existence by that point of many state and local measures aimed at that country in response to its apartheid policies.Footnote 18 A 2007 federal statute specifically allowed for state and local disinvestment from Sudan.Footnote 19 And a 2010 statute authorized state and local disinvestment from Iran.Footnote 20 Some states disinvested from Russian banks and companies after Russia’s 2022 invasion of Ukraine, and, to date, these measures have not been found to be pre-empted.Footnote 21
It is possible that some state activities will be found to be pre-empted even in the absence of a conflict with a statute or agreement if the laws or activities unduly interfere with either the national government’s authority to regulate commerce or its ability to conduct foreign relations. The US Supreme Court has construed the Constitution’s grant of authority to Congress to regulate domestic and international commerce as implicitly pre-empting some state laws and activities under a doctrine known as the “dormant Commerce Clause.”Footnote 22 The court has also held that some state laws or activities will be pre-empted if they have a direct impact on foreign affairs under a doctrine known as “dormant foreign affairs preemption.”Footnote 23 The current scope and viability of this latter doctrine is uncertain, and the US Supreme Court has generally seemed more sceptical in recent years of dormant pre-emption, at least in the absence of discrimination against other states or nations.Footnote 24 This is true even in the domestic context. Recently, for example, the court declined to invalidate a California law that imposed animal treatment requirements on pork sold in the state, despite the fact that the law would primarily affect producers of pork in other states.Footnote 25
Federalism is also relevant to US foreign affairs in a variety of other ways that do not implicate federal pre-emption. Most actions by non-US citizens inside the United States, involving matters such as contracts, property rights, and criminal responsibilities, are regulated under state rather than federal law. The states have their own judicial systems, and their courts can and do hear cases relating to foreign affairs. The national government also often takes federalism into account when negotiating treaties, and the Senate does so when attaching conditions to its consent to treaties.Footnote 26 Compliance with some international obligations is further complicated by federalism, something illustrated by the US Supreme Court’s decision in Medellin v Texas, which held that state courts were not obligated to comply with a decision by the International Court of Justice mandating hearings for certain individuals convicted of state crimes.Footnote 27
B. Article I, Section 10
Another way in which the US Constitution sought to ensure national control over foreign relations was by disallowing the states from engaging in certain foreign relations activities. As noted above, Article I, section 10, of the Constitution disallows states from, among other things, entering into treaties, and it requires that they obtain congressional consent in order to enter into “any Agreement or Compact” with another state or foreign power. This latter provision is often referred to as the “Compact Clause.” The Constitution does not explain the difference between treaties and agreements/compacts, and the dividing line between these categories has long been uncertain.Footnote 28
There have been several theories throughout history about the difference between treaties and agreements and compacts. One theory draws upon distinctions drawn by the Swiss publicist Emmerich Vattel, whose international law treatise (published in 1758) was well known to the founding generation in the United States. In his treatise, Vattel contrasted “treaties” from “agreements, conventions, and arrangements.” Whereas treaties, in Vattel’s classification, are entered into by sovereigns “either in perpetuity or for a considerable length of time,” agreements, conventions, and arrangements “are fulfilled by a single act and not by a continuous performance of acts.”Footnote 29 In other words, Vattel viewed treaties as ongoing arrangements and other international agreements as one-time resolutions.
However, the eminent US jurist Joseph Story thought that using the Vattel categorization for this purpose was “at best a very loose, and unsatisfactory exposition,” and he suggested that the distinction in Article I, section 10, might instead turn on the importance and subject matter of the agreement. In particular, Story surmised that Article I, section 10, might have been distinguishing between “treaties of a political character,” such as treaties of alliance or those granting general commercial privileges, and agreements addressing “mere private rights of sovereignty; such as questions of boundary; interests in land, situated in the territory of each other; and other internal regulations for the mutual comfort, and convenience of States, bordering on each other.”Footnote 30
A plurality of the US Supreme Court endorsed the Vattel distinction in a 1840 decision, Holmes v Jennison. Footnote 31 The issue in this case was whether the state of Vermont was precluded by Article I, section 10, from agreeing to extradite a Canadian citizen to Canada after he had been indicted in Québec for murder. This issue arose before there was a federal extradition statute and at a time in which there was no operative extradition treaty between the federal government and Great Britain, which handled Canada’s foreign policy. Four justices, in an opinion by Chief Justice Roger Taney, concluded that, although Vermont’s agreement with Canada was not a treaty, it was a compact or agreement that required congressional approval. In addition to relying on Vattel, the plurality emphasized the importance of formal characteristics in distinguishing between treaties and other agreements, noting that, whereas a treaty is “an instrument written and executed with the formalities customary among nations,” a compact or agreement could be less formal and, in fact, could even be a verbal agreement. A fifth justice agreed that an extradition agreement between Vermont and Québec would violate Article I, section 10, but he doubted that there had been such an agreement. On remand, the Vermont Supreme Court found that there was in fact such an agreement, which it held violated Article I, section 10.Footnote 32
Besides Holmes, there is little case law explaining the difference between a “treaty” that states can never enter into and an “agreement or compact” that they can enter into with congressional approval. In an 1877 decision, however, the US Supreme Court observed that the agreement among the Confederate states during the Civil War did not give the Confederacy a legal status because “the Constitution of the United States prohibits any treaty, alliance, or confederation by one state with another.”Footnote 33 Under this analysis, an agreement by a state to form a military alliance with a foreign power or to form a common government — scenarios unlikely today but that would have seemed like realistic concerns to the constitutional founders — would presumably be viewed as a treaty that is completely off-limits.
In practice, the distinction between treaties and agreements/compacts probably does not matter that much today when considering the propriety of state international agreements. If there is no congressional consent, then, as in Holmes, a state agreement is improper if it is either a treaty or an agreement or compact within the meaning of the clause. And if Congress has consented to a state agreement with a foreign nation, it seems unlikely that courts would invalidate the agreement on the ground that it is a treaty forbidden to the states, especially given the uncertain nature of the distinction between the categories. Indeed, in this situation, it is very possible that courts would treat the distinction as a non-justiciable political question to be left to Congress’s determination.Footnote 34
In practice, what has mattered is whether a state agreement is neither a treaty nor an agreement or compact. The plurality decision in Holmes can be read to suggest that, if a state agreement with a foreign nation is not a treaty, then it must be an agreement or compact. In fact, though, it has long been accepted that not all state agreements with foreign nations qualify as even agreements or compacts that need congressional approval. For that distinction — that is, between agreements that require congressional approval and those that do not — Story’s analysis has been influential, even though he offered it as a distinction between treaties and agreements/compacts. Story’s influence, however, has been indirect, relating to a different part of Article I, section 10.
In addition to addressing international agreements, Article I, section 10, says that states must obtain congressional consent in order to conclude agreements or compacts with other states. The US Supreme Court has held, however, that not all agreements between states fall within this requirement. In Virginia v Tennessee,Footnote 35 the court, drawing upon Story’s distinction of treaties from compacts/agreements, stated that congressional consent is required only for agreements between states that “tend[] to the increase of political power in the states, which may encroach upon or interfere with the just supremacy of the United States.”Footnote 36
The court has reaffirmed this approach in subsequent decisions involving inter-state agreements. In these decisions, the court has emphasized that the form of the agreement is not dispositive; rather, the issue is whether the agreement enhances state power at the expense of federal supremacy. In US Steel Corp. v Multistate Tax Comm’n, for example, the court reasoned that a multi-state tax compact, which created an administrative commission, did not need to be approved by Congress because “[t]his pact does not purport to authorize the member States to exercise any powers they could not exercise in its absence. Nor is there any delegation of sovereign power to the Commission; each State retains complete freedom to adopt or reject the rules and regulations of the Commission. Moreover, … each State is free to withdraw at any time.”Footnote 37
In Northeast Bancorp, Inc. v Bd. of Governors of Fed. Reserve Sys., the court was sceptical that two state statutes that regulated regional bank acquisitions on a reciprocal basis amounted to an “Agreement or Compact” for the purposes of Article I, section 10, reasoning that “several of the classic indicia of a compact are missing.”Footnote 38 In particular, the court noted that “[n]o joint organization or body has been established to regulate regional banking or for any other purpose. Neither statute is conditioned on action by the other State, and each State is free to modify or repeal its law unilaterally. Most importantly, neither statute requires a reciprocation of the regional limitation.”Footnote 39 The court also concluded that, in any event, as long the state statutes complied with a federal statute that authorized state regulation in this area, they “cannot possibly” infringe federal supremacy and that, if they did not comply with federal statutory limitations, they would be subject to federal pre-emption.Footnote 40
Because inter-state agreements and agreements between states and foreign governments are mentioned in the same clause of Article I, section 10, commentators have generally assumed that the analysis from Virginia v Tennessee, which relies on Story’s distinction, applies to state agreements with foreign nations. The Restatement (Third) of Foreign Relations Law, for example, states, citing Virginia, that “states may make international agreements without the consent of Congress as long as the agreements do not ‘impinge upon the authority or the foreign relations of the United States.’”Footnote 41 The State Department also has assumed that the approach in Virginia is relevant to determining whether state international agreements need congressional approval.Footnote 42 So, too, have a number of state attorneys general.Footnote 43 This approach, it should be noted, is both lenient and indeterminate, and one might reasonably question whether a stricter and more precise standard is warranted in the international context.Footnote 44
2. Lack of congressional involvement
Congress has often acted to approve or disapprove state compacts with other states,Footnote 45 but only occasionally has it been involved in deciding whether to approve state agreements with foreign governments. The first time it did so was in 1870 when it approved a compact between the state of New York and Canada to construct a Niagara River bridge.Footnote 46 But, since that time — in a period of more than 150 years — there have been only about a dozen examples of congressional action on state international agreements.Footnote 47 And the agreements approved by Congress have concerned just a few subjects: bridges, fire-fighting, highways, and emergency management.Footnote 48 This means that states have often entered into agreements with foreign governments that have not been approved by Congress.
In the early twentieth century, the executive branch tended to oppose unapproved state agreements. In 1909, the US attorney general advised the State Department that the state of Minnesota could not enter into an agreement concerning the construction of a dam on the Canadian-US border unless it obtained Congress’s consent.Footnote 49 According to the attorney general, Article I, section 10, of the Constitution “prohibits a State from making any kind of an agreement [on its own] with a foreign power.”Footnote 50 In 1936, California asked the State Department whether it could make an agreement with the Mexican territory of Baja, California, to reciprocally exempt motor vehicles from registration and payment of fees, and the department’s legal adviser replied that such an arrangement would, at minimum, require the consent of Congress and might even infringe on the national government’s treaty power.Footnote 51 In 1937, the State Department suggested that the state of Florida could not enter into an agreement with Cuba to promote trade even if it obtained congressional approval.Footnote 52
But this executive branch opposition faded, and state agreement making without congressional consent grew after the Second World War with the rise in globalization of commerce and travel. At times, like the French police chief’s professed lack of awareness of gambling at Rick’s Café in the movie Casablanca, there seems to have been a certain amount of willful blindness by the executive branch to this growing practice. In 1924, the State Department reported that it had no information on the conclusion of any treaty or agreement between a state of the United States and a foreign government.Footnote 53 In 1967, an observer remarked that “[t]he policy of not noticing such agreements seems to continue to this date and the present author is unable to document agreements known to exist.”Footnote 54 Some of this willful blindness was made easier by the fact that it preceded the Internet age, so it was less likely that these agreements were widely known. In recent years, the State Department has had to acknowledge its general awareness of the robust state practice. In 2001, the State Department’s legal adviser acknowledged that the department was “aware that U.S. states often conclude various arrangements with foreign powers without congressional consent.”Footnote 55 But it has been passive with respect to this development and has sometimes insisted that it is up to Congress, not the executive branch, to object.
In early 2001, Senator Byron Dorgan from North Dakota wrote to the State Department complaining about a memorandum of understanding (MOU) that Missouri had signed with the Canadian province of Manitoba. In the MOU, Missouri and Manitoba agreed to “work cooperatively to the fullest extent consistent with law and existing treaties” in their efforts to oppose water transfers between the Missouri River and the Hudson Bay watersheds, due to their concern about the introduction of invasive species. Senator Dorgan’s state would benefit from the water transfers, and he objected. After many months, the State Department’s legal adviser, William Taft, responded to the senator by noting that “the Constitution does not specifically assign responsibility for interpretation or enforcement of [the Compact Clause] to the Executive branch of the federal government.”Footnote 56 Taft also observed that, while “it is not uncommon for states of the United States to consult with the Department of State when they are considering entering into arrangements with a foreign power that may engage these interests,”Footnote 57 this had not happened for the MOU in question. Taft attached a memorandum to his response describing “some of the considerations that the Department would have raised if it had been consulted.”Footnote 58
The memorandum that Taft attached noted that the view articulated by Taney CJ in Holmes that all state agreements with foreign governments require congressional consent “has not been widely supported.”Footnote 59 The memorandum relied instead on Virginia v Tennessee for the proposition that only agreements that “would increase the political power of the states in such a way as to interfere with the supremacy of the federal government require congressional consent.” The State Department is aware, the memorandum explained, that states often conclude agreements with foreign powers: “When [these agreements] are called to the Department’s attention, such arrangements have generally been analyzed under the Virginia standard, with particular attention to whether such texts would interfere with the President’s foreign relations responsibilities.”Footnote 60 Some of the factors to be considered, the memorandum suggested, are attributes like whether the agreement imposes binding obligations, limits withdrawal, has various formal attributes of an agreement, and sets up a joint body or organization. This multi-factor approach is not very determinate, and, in any event, the State Department has not shown any inclination to actively police state international agreements and nor has Congress. Indeed, it is telling that Senator Dorgan appealed to the State Department rather than to the body in which he served — that is, Congress.
3. Litigation over the California-Québec agreement
The phenomenon of international agreements by US states assumed new prominence during the Trump administration, which sued to challenge a climate change-related agreement between California and Québec. The agreement was an outgrowth of a regional organization — the Western Climate Initiative — formed in 2007 by the governors of California and other western states and the premiers of several Canadian provinces. In 2010, this organization had recommended a regional “cap-and-trade” program, whereby there would be a cap on the overall emissions of regulated entities, emissions allowances would be given out, and there would be an ability to trade the allowances. In 2011, the organization established a non-profit corporation — Western Climate Initiative, Incorporated (WCI) — to provide administrative and technical support for such a program.Footnote 61
Both California and Québec established cap-and-trade programs, and, then in 2013, they agreed to link the programs by, for example, conducting joint auctions for the purchase of allowances. This linkage agreement was organized, like a treaty, into chapters and articles, and it has provisions concerning matters such as withdrawal, amendments, and dispute resolution.Footnote 62 It also frequently uses the mandatory word “shall.” While the agreement says that each party has the sovereign right to modify its regulations, it also says that termination of the agreement requires the unanimous consent of the parties and that the termination shall not be effective until twelve months after such consent. In 2017, the agreement was modified to add Ontario to the linkage,Footnote 63 although Ontario canceled its cap-and-trade program the following year and dropped out of the program.
These efforts took place against the backdrop of international negotiations over the Paris Agreement on climate change.Footnote 64 In 2016, during the Obama administration, the United States joined the Paris Agreement. The administration did so, it should be noted, without seeking congressional approval, claiming that parts of it were authorized by an earlier treaty (the 1992 United Nations Framework Convention on Climate Change) and that the core emissions reduction obligation in the convention was non-binding and, thus, did not require legislative approval.Footnote 65 Obama’s successor, Donald Trump, was opposed to the Paris Agreement and, in 2017, announced that the United States was withdrawing from it. Because of a provision in the Paris Agreement that limited withdrawal, the United States’ exit from it did not take effect until 2020. Meanwhile, the Trump administration sued California over its cap-and-trade agreement with Québec, arguing that the agreement violated Article I, section 10, of the Constitution and was also pre-empted by federal law. A federal district court rejected these arguments.Footnote 66 The government appealed, but the subsequent Biden administration decided not to continue challenging California’s action. President Joe Biden also had the United States rejoin the Paris Agreement.
In rejecting the administration’s Article I, section 10, argument, the district court first reasoned that the California-Québec agreement was not a “treaty,” noting that it was not an alliance for purposes of peace and war, a general trade agreement, or an agreement that entailed a cession of sovereignty. On the last point, the court pointed out that each party had adopted its own emission reduction targets and applied its own regulations in administering the cap-and-trade programs and that each party was free to modify or repeal its program. As for whether the agreement was an “Agreement or Compact” requiring congressional approval, the court noted that the parties’ cap-and-trade programs could operate independently, that the agreement did not impose a regional limitation, and that WCI did not exercise regulatory authority over the parties. Finally, the court emphasized that the agreement did not contain any enforceable prohibition on unilateral modification or termination of a party’s regulations: “[T]he simple fact that California retains the power to modify its enacting regulations, means unilateral termination of California’s participation in the Agreement is possible.”Footnote 67
In a separate opinion, the court also rejected the Trump administration’s pre-emption arguments. The court first concluded that the agreement did not conflict with any federal statute or treaty. Next, it held that the agreement was not pre-empted by President Trump’s decision to withdraw from the Paris Agreement, reasoning that there was no conflict with a “clear and express foreign policy.” A mere “intent to negotiate for a ‘better deal’ at some point in the future” is not enough to pre-empt state law. The court also concluded that the agreement was not subject to dormant pre-emption. Even though the agreement extended beyond an area of traditional state responsibility, the court concluded that it did not unduly intrude on the national government’s authority over foreign affairs. Among other things, the court said there was an “absence of concrete evidence that the President’s power to speak and bargain effectively with other countries has actually been diminished.”Footnote 68
The district court’s conclusions, especially with respect to Article I, section 10, are debatable. The agreement between California and Québec concerns an important topic that overlaps with issues of national policy. It is also a formal, ongoing arrangement that uses mandatory language throughout. The district court’s permissive approach largely converts the Constitution’s requirement of affirmative congressional approval for state international agreements to an allowance of such agreements in the absence of congressional disapproval.Footnote 69 While such a shift might draw support from what is now extensive governmental practice (including national government inaction),Footnote 70 the arguments for judicial deference to such practice are more complicated in the federalism context than in the separation of powers context. Among other things, the patterns of practice in the federalism context are less likely than in the separation of powers context to reflect an institutional bargain concerning constitutional authority, and the need for deference may also be lower in the federalism context because the courts are not being asked to sit in judgment on co-equal institutions.Footnote 71 For state international agreements, the national government’s general passivity to date may simply reflect the fact that the agreements have not yet raised serious foreign relations difficulties for the national government.Footnote 72
Although only from a single district court, the decision to uphold the California-Québec agreement is important because there are few other judicial precedents in this area.Footnote 73 The decision is likely to further encourage states and localities to make agreements without seeking congressional approval.Footnote 74
4. Rise of sub-national agreements and potential for conflict
Unlike agreements made at the national level, there is no formal system in the United States for the reporting and publication of state-level agreements. As a result, at least until recently, it has been difficult to know much about the scale and nature of this practice. A 1974 study prepared for the State Department found 766 active and ongoing “interactions” between US states and Canadian provinces, with interactions defined to include agreements, understandings, and arrangements.Footnote 75 The study showed that state-provincial interaction was “pervasive in scope, extending to all functional areas of governmental activity.” More than twenty years later, a book on the role of states in foreign affairs reported that “[a]ll states have entered into international agreements, accords, or pacts with national and subnational governments abroad” and that “[o]ver 400 agreements currently exist between the states and Canadian provinces.”Footnote 76
In a 2010 article, which did not purport to be comprehensive, Duncan Hollis identified “over 340 [international agreements] concluded by forty-one U.S. states since 1955.”Footnote 77 The unapproved agreements, as Hollis noted, covered a vast range of topics, such as coordination on roads, police cooperation, border control, local trade cooperation, education exchanges, and conservation measures. Recently, Ryan Scoville has offered a more comprehensive (but still incomplete) empirical picture.Footnote 78 Based on materials that he obtained through open records requests to the various states, Scoville identified over six hundred agreements currently in force, totalling roughly three thousand pages, a finding that (as he notes) almost certainly understates the total number. His data indicates that state agreement making started increasing substantially around the year 2000 and that China and its provinces and cities are now the primary agreement partner, followed by Canada and its provinces.Footnote 79
As noted in in the last section, the Trump administration unsuccessfully challenged a climate change-related agreement between California and Québec. That agreement is one of many sub-national agreements in recent years relating to climate change. In 2006, California entered into an agreement with the United Kingdom to limit emissions.Footnote 80 In 2007, ten US states joined ten European nations, the European Commission, two Canadian provinces, and New Zealand to form an “International Carbon Action Partnership” to promote cap-and-trade carbon markets to combat global warming.Footnote 81 In 2014, California entered into a MOU with agencies of Mexico to address climate change.Footnote 82 In 2018, the California Energy Commission entered into a MOU with Scotland to develop the use of wind energy.Footnote 83 In 2021, California signed a joint declaration with New Zealand and Québec on cooperation in the fight against climate change, with the hope that it could lead to New Zealand’s emission-trading scheme joining the established Québec-California market partnership.Footnote 84 In 2022, California renewed a MOU with China to enhance cooperation in addressing climate change and promoting the use of clean energy.Footnote 85 In 2023, the state of Washington’s Department of Ecology launched a public consultation process to explore linking Washington’s cap-and-invest program to the systems of California and Québec.Footnote 86
Climate change is just one of many topics for which there are state international agreements. As Hollis has noted, these agreements today cover a wide array of topics, “including agriculture, climate change, education, energy, environmental cooperation, family support, hazardous waste, homeland security, investment, military cooperation, pollution, sister-state relations, tourism, trade, transportation, and water issues.”Footnote 87 Moreover, although California is an especially active player in this realm, all the US states sometimes enter into international agreements.Footnote 88 This extensive practice of state international agreement making seems surprising from the perspective of the text of the US Constitution and the original intentions of its founders, so it is a good example of constitutional evolution. For the most part, the national government has not resisted this development, which is probably because the agreements generally do not cause foreign relations problems for the country. Other nations do not typically object to more international cooperation, and, thus, the agreements tend not to generate obstacles to the national government’s management of foreign affairs.Footnote 89
If anything, the federal government has promoted rather than opposed sub-national engagement with foreign governments. For example, US cities often form “sister city” relations with cities in other countries for the purposes of promoting trade, tourism, and educational and cultural exchange, and this engagement has been facilitated by Sister Cities International, a non-profit organization based in Washington, DC, that was originally established by President Dwight Eisenhower. Its network now includes over two thousand cities, states, and counties across more than 140 nations.Footnote 90 These sister-city relationships are embodied in agreements between the relevant jurisdictions. In 2022, the Biden administration went further and created in the State Department a “Special Representative for Subnational Diplomacy,” whose office “lead[s] and coordinate[s] the State Department’s engagement with mayors, governors and other local officials in the United States and around the world.”Footnote 91 Congress expressed support for this development in legislation, observing that the new office “will play a critical role in leveraging the Department’s resources to support State and municipal governments in conducting subnational engagement and increasing cooperation with foreign allies and partners.”Footnote 92
Despite this encouragement from the executive branch and Congress, there could be more conflicts between states and the federal government in the years ahead. National partisanship has filtered down to state governments, which means that these governments sometimes purposely position themselves to be at odds with a particular administration’s policies. In addition, some state governors aspire for national office, which can lead them to stake out independent foreign policy positions. At the same time, foreign governments appear to be increasingly targeting sub-national governments as a way of working around the national government. This has been true of China, for example, as Scoville has noted:
[S]tates have entered into a collection of instruments with national, provincial, and municipal authorities from the People’s Republic of China (PRC) for the express purpose of promoting technology transfer in a number of strategically sensitive fields of innovation, including information technology, nanotechnology, aerospace, biotechnology, and semiconductors. Most of these instruments appear to have been adopted not only without federal approval or public disclosure, but also at the initiative of the Chinese government. This suggests a coordinated, ongoing, and perhaps even intensifying PRC campaign to leverage relations with U.S. states to expand influence and acquire cutting-edge American technology, despite federal efforts to preserve U.S. technological leadership.Footnote 93
The national government has specifically warned states that, “as tensions between Beijing and Washington have grown, the government of the People’s Republic of China (PRC) under President Xi Jinping has increasingly sought to exploit these China-US subnational relationships to influence US policies and advance PRC geopolitical interests.”Footnote 94
Not to be outdone, Taiwan has also been deepening its engagement with US states.Footnote 95 Other nations may also be targeting US states and localities. Recently, for example, the United Kingdom entered into trade-related agreements with US states at the same time that it was attempting to negotiate a free trade agreement with the national government.Footnote 96 The potential for conflicts with national policy would be even greater if states started making agreements with countries like Iran and North Korea, although the arguments for pre-emption would also be stronger in these instances in light of the national government’s sanctions against those regimes. Moreover, we know that states sometimes take actions that can generate international friction. Recently, for example, Montana purported to ban the social media platform TikTok, which is owned by a Chinese-controlled company, an action that quickly led to litigation.Footnote 97 Florida, meanwhile, recently purported to prohibit individuals who are domiciled in China and certain other countries from owning buildings or land in the state, again something that prompted suit.Footnote 98 Before these actions, some US states (and others) had sued China for the COVID pandemic, an effort that to date has been blocked by a federal statute, the Foreign Sovereign Immunities Act. Footnote 99 States in recent years have also asserted positions relating to immigration that are out of sync with the national government’s approach — for example, conservative states attempting to bolster enforcement of immigration law during the Obama administration and liberal states and cities claiming to be “sanctuary jurisdictions” during the Trump administration.Footnote 100 It is thus not difficult to imagine conflicts developing between state agreement making and national policies.
5. The binding versus non-binding distinction
Another reason that state international agreements have not generated much opposition to date from the national government is that many of them are not legally binding. That is, they do not purport to create enforceable obligations under international or domestic law. Many take the form of “memoranda of understanding” and the like that are intended merely to guide cooperation rather than to lock the parties into commitments that they might otherwise be inclined to breach. The district court in the California-Québec case emphasized this point about the cap-and-trade agreement at issue there, noting that “there is no enforceable prohibition on unilateral modification or termination.”Footnote 101 The 2001 State Department memorandum referenced above took the position that, although whether an agreement is binding is an important consideration in whether an agreement must be approved by Congress, it is not a prerequisite. But this point is disputed, and states have maintained that they do not need to submit non-binding agreements to Congress for its approval. In any event, the executive branch is much less likely to object to agreements if they are non-binding.Footnote 102 The department has in fact offered to provide guidance to states in their drafting of agreements to help ensure that the agreements are indeed not binding.Footnote 103
It is worth noting that some state international agreements by their terms appear to impose binding reciprocal obligations.Footnote 104 In fact, as discussed earlier, many aspects of the California-Québec agreement are written in terms that sound binding.Footnote 105 Even when a state international agreement is labeled as a MOU or joint declaration, it will not necessarily mean that it is non-binding. In his recent study, Scoville found that approximately one-fourth of the state international agreements used binding language like “shall.”Footnote 106 Binding agreements can potentially implicate issues of national responsibility that should be of potential concern to the national government.Footnote 107 In part for this reason, guidelines developed by the Inter-American Juridical Committee of the Organization of American States in 2020 suggest that nations “have procedures by which they can assure appropriate authorization for any institutions (whether government ministries, sub-national units, or both) with the capacity to conclude a treaty governed by international law.”Footnote 108
Even when the agreements are genuinely non-binding, it may be artificial to distinguish sharply between binding and non-binding agreements. In practice, these two types of agreements may have a similar form and operate in similar ways. In neither situation are the parties likely to try to bring each other to court (either domestic or international) over a violation, and probably cannot do so even if the agreement is binding, due to limitations such as sovereign immunity. But the parties may nevertheless feel obligated to comply with both types of agreements and for similar reasons — for example, because they desire reciprocity, have made investments in the relationship, worry about their reputations for compliance, have implemented the obligations in their internal law, and the like.Footnote 109
This is not the only example in which making an international agreement non-binding may avoid domestic legal constraints. The US national government does this as well: the executive branch has only limited authority to make agreements without congressional approval.Footnote 110 But the requirement of congressional approval is thought to apply only to binding agreements.Footnote 111 The federal executive branch often makes agreements that are non-binding, sometimes to avoid legislative approval requirements. A prominent example is the Iran nuclear deal (also known as the Joint Comprehensive Plan of Action) that the Obama administration concluded, along with several other nations, in 2015.Footnote 112 Somewhat similarly, the Obama administration justified its conclusion of the Paris Agreement on climate change without congressional approval in part because the emissions reduction obligation in the agreement was non-binding.Footnote 113 Moreover, although Congress has long mandated reporting and publication of international agreements made by the executive branch,Footnote 114 this mandate until recently was construed to apply only to binding agreements.Footnote 115 In December 2022, Congress passed legislation mandating for the first time the reporting and publication of non-binding agreements made by the executive branch if they “could reasonably be expected to have a significant impact on the foreign policy of the United States” — a requirement that becomes effective in September 2023.Footnote 116 But there is not currently any such mandate for international agreements made by state governments.
There have been proposals in recent years to have the State Department maintain a database of these agreements, but Congress has not enacted such a requirement,Footnote 117 and, in any event, its efficacy would depend on state cooperation. Congress could set up a registry system, with perhaps a safe harbour provision, promising, for example, that state agreements submitted and not overturned within a certain period would get protection from challenges.Footnote 118 But given that almost none of the agreements are being challenged anyway, such a system might not provide enough of an incentive, and states might be wary of highlighting their agreement practice in ways that might trigger national government objections. Another option would be for Congress to provide funding to the states to support more transparency, something that might provide a more tangible incentive. State governments could of course adopt transparency mandates on their own initiative; it is in the interest of state populations, after all, to know what agreements their governments are making on their behalf.Footnote 119
This issue of how to ensure sufficient accountability for non-binding agreements is increasingly a matter of international concern. Non-binding agreements offer parties greater flexibility in their commitments, allowing for adjustments if the conditions or their interests change. But the use of such agreements can also undermine government accountability because the agreements are not typically subject to the domestic rules concerning legislative approval, reporting, and publication that apply to binding agreements. The growth of these agreements also has potentially profound implications for the field of international law, which has traditionally been organized around binding obligations.Footnote 120 Recognizing the importance of the development, the United Nations’ International Law Commission has placed the topic of non-binding international agreements on its long-term agenda.Footnote 121 The comparative and international discussions of this topic have so far tended to focus on national agreements,Footnote 122 but, as this article has shown, it is important to consider the vibrant sub-national practice as well.
6. Conclusion
For a variety of reasons, Article I, section 10, of the US Constitution does not do much work today in limiting state international agreements. States often make these agreements but almost never seek congressional approval, and Congress, the executive branch, and the courts do not typically object. The main check on this sub-national practice is the possibility of federal pre-emption, but, at least to date, the pre-emption doctrines have also not presented much of an obstacle. In general, the rise of state international agreements is likely a positive development because the agreements allow for more extensive international cooperation in ways that are tailored to local interests and conditions.Footnote 123 As a scholars’ amicus brief noted in the California-Québec case, “[i]n today’s interconnected world, the need for coordination has become far greater and less spatially focused than during the nineteenth century,” and this shift has “led to more horizontal, vertical, and diagonal coordination among different levels of government.”Footnote 124 Moreover, it has become more difficult in recent years for the national government to conclude international agreements due to partisan and other limitations,Footnote 125 so these state-level agreements may help fill a needed gap. But both the lack of transparency and the potential for federal-state conflicts are likely to require attention going forward.
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