Tariffs are at the center of President Donald J. Trump’s “America First Trade Policy” in his second term.Footnote ¹ Citing emergency and national security concerns, the Trump administration has imposed double- and triple-digit percent tariffs on imports from nearly every country in the world.Footnote ² By April 2025, the Trump tariffs had increased the average weighted U.S. tariff to 23 percent—a ten-fold increase from a year prior.Footnote ³ In addition to the economic and business ramifications of this policy, two major legal and political moves have followed the president’s threats and unpredictable tariff policies: first, importers and other groups have sought relief from these policies in the U.S. courts, alleging that the president’s wholesale remaking of tariff rates violates U.S. law; and second, governments across the globe have entered into negotiations with the United States, pursuing agreements to shield them from the worst of the tariffs. Both moves have prompted questions about the reach of the president’s foreign commerce authority and the separation of trade law powers in U.S. foreign relations and constitutional law.

Article I, Section 8 of the U.S. Constitution grants the Congress the power to regulate commerce with foreign nations and to levy duties.Footnote ⁴ By contrast, the president’s power over commerce and taxes is purely statutory.Footnote ⁵ Over the last century, Congress has delegated authority to the executive branch to increase tariff rates under certain circumstances, and has typically subjected those regulatory changes to judicial review.Footnote ⁶ For instance, U.S. trade remedies statutes allow importers to petition the U.S. Department of Commerce and the U.S. International Trade Commission to counteract unfair trade practices or address import surges that harm domestic industries by increasing tariff rates to those imports.Footnote ⁷ Each year, dozens of importers use these highly technical tools to pursue relief on products from roughly thirty different countries in more than twenty different industries.Footnote ⁸ Apart from trade remedies, a handful of statutes, such as Section 232 of the Trade Expansion Act of 1962 and Section 301 of the Trade Act of 1974, grant the president discretion to impose trade restrictions, including tariffs, if he finds certain conditions are met. However, the executive branch has rarely relied on these authorities to impose tariffs of any significance on imports to the United States in the last fifty years, and especially over the last thirty years since the creation of the World Trade Organization (WTO). That historical fact makes the Trump administration’s implementation of new tariffs on most products from nearly every country especially striking.

The Trump 2.0 tariffs raise legal questions under both U.S. and international law, but the nature of the evaluation under each legal system is different. The issues facing U.S. courts include whether the administration has satisfied the prerequisites in the statutes it has invoked, as well as any applicable administrative procedures; whether those statutes are both capacious enough to authorize President Trump’s actions and sufficiently constrained to satisfy constitutional limits on congressional delegations; and whether any concerns about statutory limits are overridden by the president’s national security and foreign affairs prerogatives. These are issues of authority and method: does U.S. law authorize the president to impose these tariffs, and if so, has the president satisfied the preconditions set out in U.S. law to impose them? By contrast, the issue under international law is whether the tariff increases are consistent with WTO rules and rules set out in U.S. free trade agreements (FTAs). That evaluation is one focused on the substance of the laws and the tariff measures. This Essay addresses the former while another contribution to this special issue addresses the latter.Footnote ⁹ Additional contributions discuss how nations, especially in Africa and Asia, have responded to the tariffs.Footnote ¹⁰

The president’s most impactful tariff action in his first six months in office has been his imposition of what have been called “worldwide tariffs.”Footnote ¹¹ On April 2, the president announced a 10 percent tariff on products from all countries and additional tariffs that vary by country of origin.Footnote ¹² The president has claimed that these all-encompassing tariffs are authorized under the 1977 International Emergency Economic Powers Act (IEEPA).

IEEPA provides the president with certain extraordinary authorities that he may use to “deal with any unusual or extraordinary threat, which has its source in whole or substantial part outside the United States, to the national security, foreign policy, or economy of the United States, if the President declares a national emergency with respect to such threat.”Footnote ¹³ In this instance, the president declared an emergency regarding the “lack of reciprocity in our bilateral trade relationships, disparate tariff rates and non-tariff barriers, and U.S. trading partners’ economic policies that suppress domestic wages and consumption, as indicated by large and persistent annual U.S. goods trade deficits.”Footnote ¹⁴

Having made an emergency declaration, IEEPA empowers the president, in relevant part, to:

In addition to these global measures, the administration has implemented tariffs that are country- and product-specific. In February, also relying on IEEPA, President Trump announced the imposition of so-called “trafficking” tariffs on products from some of the United States’ biggest trading partners: Canada, China, and Mexico, referring to an “unusual and extraordinary threat” from those governments’ failures to take sufficient actions to address unlawful migration to the United States and to prevent the entry of illicit drugs into the United States.Footnote ¹⁶ Similarly, the White House in March issued an executive order in which it authorized the secretary of state to determine whether imports to the United States from any third country found importing oil from Venezuela ought to be subject to a 25 percent tariff.Footnote ¹⁷ In August, President Trump proclaimed an additional 25 percent tariff on most imports from India in response to India’s continued purchase of oil and gas from Russia, with Russia’s invasion of Ukraine serving as the predicate emergency.Footnote ¹⁸ The Trump administration has also imposed an additional 40 percent tariff under IEEPA (on top of the 10 percent tariff applicable to all countries) on goods from Brazil due to Brazil’s prosecution of its former president Jair Bolsonaro under IEEPA.Footnote ¹⁹

IEEPA is exceptional in that it does not allocate any role to executive branch agencies or require any procedure apart from a declaration of an emergency by the president, a discretionary determination.Footnote ²⁰ As a consequence, the president can act immediately under IEEPA.

By contrast, the special tariffs imposed during President Trump’s first term were based on delegations that first require an investigation and findings by an agency. These statutes enable the executive branch to raise tariffs when an agency identifies a threat to the U.S. economy from another government’s actions or a threat to U.S. national security arising from the imports of a particular product.Footnote ²¹ The administration has deployed these powers again in its second term, in addition to its IEEPA-premised actions. For example, the administration has relied on Section 232 of the Trade Expansion Act of 1962 to increase the duties on imports of steel and aluminum and their derivative products from all countries, as well as to impose new duties on automobiles and certain automobile parts and copper.Footnote ²² Section 232 permits the president to “adjust imports” of an article where the secretary of commerce finds that the article is being imported “in such quantities or under such circumstances as to threaten to impair the national security.”Footnote ²³ Additionally, in the first six months of the second Trump term, the administration has turned to Section 232 as the basis for ongoing investigations into imports of timber and lumber, semiconductors, pharmaceuticals, trucks, critical minerals, commercial aircraft, jet engines, polysilicon, and unmanned aircraft systems.Footnote ²⁴

Relying on Section 301 of the Trade Act of 1974, the Trump administration has threatened additional tariffs on products from countries imposing digital services taxes ^{Footnote 25} and on countries engaged in unfair trade practices regarding fishing.Footnote ²⁶ Section 301 permits the Office of the U.S. Trade Representative (USTR) to impose duties or other import restrictions where the USTR finds that an act, policy, or practice of a foreign country “is unreasonable or discriminatory and burdens or restricts [U.S.] commerce.”Footnote ²⁷ The Trump administration relied on Section 301 during his first term to impose tariffs on most imports from China, tariffs that the Biden administration continued and even increased with respect to some products.Footnote ²⁸

The Trump administration’s use of these so-called “three-digit tariffs”—such as those premised on Sections 232 and 301—are representative of U.S. trade law’s structural dichotomy that the first Trump term laid bare: on the one hand, well-established statutory authorities enable the president to eliminate trade barriers through negotiations with U.S. trading partners;Footnote ²⁹ on the other hand, different, previously lesser-used authorities allow the president to erect trade barriers on an exceptional basis where the government deems doing so is necessary for U.S. economic security.Footnote ³⁰ To date the courts have largely rejected the challenges brought to the president’s tariff actions under Sections 232 and 301, a testament to the limited role for judicial review that the courts have seen with respect to the exceptional, security-driven authorities.Footnote ³¹

The president’s reliance on IEEPA in his second term has pushed this dichotomy to the breaking point. Although IEEPA has long been used as a basis for economic sanctions against foreign actors, it has not been a mainstay of the foreign commerce regulatory artillery. IEEPA does not expressly refer to duties and prior to 2025 no president had ever relied on it to impose duties.Footnote ³² Moreover, President Trump’s use of IEEPA has highlighted the lack of limits of the kind that accompanies delegated tariff-setting authority. IEEPA requires no factfinding by administrative agencies, no opportunity to comment on proposed tariff rates, no time limits on the duration of the tariffs, no limits on the tariffs that can be imposed, and imposes no time limit on the president’s ability to proclaim any changes in tariffs. Other tariff delegations include at least one, if not more, of these checks.Footnote ³³ Moreover, in taking these actions, the president has relied on IEEPA to rewrite economy-wide tariff rates to which Congress consented in implementing statutes for numerous trade treaties, including the WTO Agreements and FTAs.Footnote ³⁴

This extraordinary claim of tariff-setting power, far beyond anything Congress has delegated elsewhere, has been the basis for more than a dozen lawsuits in U.S. courts. These cases focus primarily on the scope of the president’s authority under IEEPA. At the time of writing, two trial courts have enjoined the tariffs as unlawful (or likely unlawful).Footnote ³⁵ The U.S. Court of Appeals for the Federal Circuit heard an appeal in one of these cases en banc, on an expedited basis. On August 29, 2025, that court held by a vote of 7–4 that the tariffs are unlawful, although it remanded the case to the lower court to consider the proper scope of injunctive relief.Footnote ³⁶ Shortly thereafter, the U.S. Supreme Court agreed to hear the case on an expedited basis, granting review of two questions: (1) whether IEEPA authorizes the tariffs; and (2) if it does authorize the tariffs, whether IEEPA unconstitutionally delegates legislative authority to the president in violation of the nondelegation doctrine. The Court also granted certiorari before judgment in the other case, which had been scheduled for argument at the U.S. Court of Appeals for the D.C. Circuit in September, setting both cases for argument in November.Footnote ³⁷

The plaintiffs in these cases have leveled three kinds of challenges to President Trump’s IEEPA tariffs. First, the plaintiffs in the two cases that have been decided—small businesses and a group of U.S. states—have argued that the term “regulate” in IEEPA does not include the power to levy duties through taxes or tariffs.Footnote ³⁸ As noted above, IEEPA does not use the words “tariffs,” “taxes,” or “duties.”Footnote ³⁹ The plaintiffs point out, also, that the Congress does not appear to have ever used the term “regulate” to encompass the power to tax and that interpreting it to do so would radically change the understanding of regulatory delegations throughout the U.S. Code. Because “regulate” in IEEPA also modifies actions such as “holding,” “use,” and “transfer,” the government’s interpretation would also allow the president to impose sales taxes, wealth taxes, and property taxes under IEEPA.Footnote ⁴⁰ Moreover, taxes work through incremental changes, while in IEEPA “regulate” appears in a string of verbs—such as “prohibit,” “prevent,” “nullify,” and “void”—that carry more absolute meaning. Under the doctrine of noscitur a sociis, ambiguous words in a list are typically interpreted in light of the list’s other contents.Footnote ⁴¹ Finally, the plaintiffs have pointed out that the president has a wealth of other statutory authorities he can use to impose tariffs in response to a range of situations if he stays within the limits set in those statutes. The existence of those specific authorities would be superfluous if the president could use IEEPA to impose any tariffs he wants.

Second, the plaintiffs have invoked the Supreme Court’s new “major questions doctrine.” In a series of rulings, mostly involving emergency powers deployed in response to the COVID-19 pandemic, the Court has relied on that doctrine to strike down government action that arguably falls within the scope of a broad statute but is not specifically authorized.Footnote ⁴² The doctrine has two parts. First, the courts must determine whether the government action in question is of “economic and political significance,” that is, whether it is a major question.Footnote ⁴³ If it is a major question, of the kind “that Congress would likely have intended for itself,” then Congress must have clearly authorized the government’s action.Footnote ⁴⁴ The plaintiffs have argued that the president’s tariff actions easily meet these criteria.Footnote ⁴⁵ Finally, the plaintiffs have also maintained that IEEPA should be read not to authorize tariffs to avoid constitutional concerns. Specifically, interpreting IEEPA to authorize tariffs would, in the plaintiffs’ view, lead to an unconstitutional delegation of Congress’s power to levy duties and regulate foreign commerce—a violation of the nondelegation doctrine—given the lack of any limits on the president’s actions under IEEPA.Footnote ⁴⁶

Third, the plaintiffs have raised several other alleged defects with President Trump’s orders imposing the tariffs. Some have argued that the emergencies the president has declared do not arise from an “unusual and extraordinary threat.”Footnote ⁴⁷ The United States has had a trade deficit every year since 1976, making it difficult to argue that the trade deficit is either unusual or extraordinary in any ordinary sense of those terms.Footnote ⁴⁸ Plaintiffs in these lawsuits also have maintained that the tariffs have no nexus to the underlying emergencies.Footnote ⁴⁹ It is unclear, for instance, how tariffs on goods from Canada will reduce drug smuggling.

The Trump administration has three principal counterarguments. First, the government has argued that IEEPA’s authorization to “regulate … importation” implicitly authorizes tariffs because tariffs have the effect of changing, or “regulating,” behavior.Footnote ⁵⁰ The government has also argued that the diplomatic leverage created by tariffs creates the necessary nexus with the underlying emergency by allowing it to negotiate a resolution to the underlying emergency.Footnote ⁵¹

Second, the government notes that in 1971 President Nixon relied on the Trading with the Enemy Act (TWEA), which also authorized the president to “regulate … importation,” to impose a 10 percent surcharge on imports.Footnote ⁵² In United States v. Yoshida International, Inc., the predecessor court to the Federal Circuit Court of Appeals upheld that use of authority, albeit with the caveat that “[t]o uphold the specific surcharge imposed … is not to approve in advance any future surcharge of a different nature, or any surcharge differently applied or any surcharge not reasonably related to the emergency declared.”Footnote ⁵³ The Trump administration has maintained that the president’s IEEPA-based actions ought to be upheld, citing the Nixon case as applicable precedent.Footnote ⁵⁴

The Trump administration’s third response has been that courts should uphold the president’s tariffs because of their relationship to foreign affairs. Under an approach to judicial review known as “foreign affairs exceptionalism,” courts often suspend the normal rules of interpretation that apply in the domestic context when foreign affairs are implicated.Footnote ⁵⁵ Applied here, the administration has sought to characterize the president’s actions as having constitutional underpinnings that should trigger deferential review by the judiciary.Footnote ⁵⁶

The majority opinion of the Federal Circuit Court of Appeals stopped short of saying that tariffs are never authorized under IEEPA. The majority pointed out that IEEPA does not mention tariffs,Footnote ⁵⁷ does not include the kinds of limitations found in statutes delegating tariff authority,Footnote ⁵⁸ and had never previously been used to impose tariffs.Footnote ⁵⁹ The court rejected the government’s assertion of any constitutional power for the president to set tariff rates, holding that “[a]bsent a valid delegation by Congress, the President has no authority to impose taxes.”Footnote ⁶⁰ Likewise, the court interpreted Yoshida’s holding to rest “on the limits of President Nixon’s Proclamation” and concluded that, in passing IEEPA, Congress had at most incorporated Yoshida’s limited understanding of the power conferred by the term “regulate … importation.”Footnote ⁶¹ The court also relied on the major questions doctrine, concluding that Congress would have had to clearly authorize tariffs of the size and scope of the challenged tariffs and had not done so.Footnote ⁶²

The court’s opinion was accompanied by two separate opinions. Expressing “additional views,” four members of the majority would have gone further and held that IEEPA never authorizes tariffs, for the reasons discussed above.Footnote ⁶³ The four dissenters would have held that IEEPA does authorize tariffs—accepting the government’s textual argument about the scope of the term “regulate”—and that it does so without violating the nondelegation doctrine.Footnote ⁶⁴ Common ground across all of the opinions was that the Court of International Trade (CIT) has exclusive jurisdiction over cases challenging the imposition of tariffs and that the case should be remanded to the CIT to reconsider whether its injunction against the government collecting the tariffs from any importer, not only the plaintiffs, is appropriate in light of a recent Supreme Court decision significantly narrowing the circumstances in which courts may grant so-called “universal injunctions.”Footnote ⁶⁵

In the other case consolidated for argument before the Supreme Court, the district court granted a preliminary injunction to two small businesses, concluding that the plaintiffs were likely to succeed because IEEPA does not authorize the president to impose tariffs in light of the law’s text and context, and in view of nondelegation and major questions concerns. That conclusion was also the basis for the court’s decision that it had subject matter jurisdiction. The CIT has exclusive jurisdiction over cases “aris[ing] out of any law of the United States providing for … tariffs.”Footnote ⁶⁶ As noted above, the Federal Circuit Court of Appeals concluded that the CIT has exclusive jurisdiction over cases challenging tariffs, and other district courts had concluded that the Harmonized Tariff Schedule of the United States is itself a statute providing for tariffs, thus affording the CIT exclusive jurisdiction over challenges to IEEPA tariffs even if IEEPA itself did not authorize tariffs. The D.C. district court disagreed, though, holding that if IEEPA does not authorize tariffs at all, then the CIT would not have exclusive jurisdiction over challenges to actions taken under that statute (even if such unauthorized actions took the form of tariffs).

Even if the courts were to conclude that IEEPA does not permit the president to levy tariffs, the president need only pivot to other statutes that would allow him to do so, such as Section 122 of the Trade Act of 1974, or Section 338 of the Tariff Act of 1930, or back to Section 232 and Section 301.Footnote ⁶⁷ Although those statutes have additional guardrails and limitations, and thus tend to impose greater accountability, a president could likely leverage them to achieve a similar outcome.Footnote ⁶⁸ Only Congress can close off these pathways.

Thus, a more all-inclusive approach to ending or limiting the Trump administration’s heavy use of tariffs would require congressional action to amend the statutory scheme it set out during the Cold War to clarify the scope of the president’s tariff-related authority through legislation, as some commentators have advocated.Footnote ⁶⁹ Such an intervention from Congress is unlikely, though. In April, the Senate delivered a rare rebuke to the president’s trade program by passing, by a vote of 51–48, a measure that would terminate the national emergency on illicit drugs with respect to Canada—a first step to reining in one set of tariffs.Footnote ⁷⁰ The resolution did not make further progress, however, and no comprehensive legislation has been introduced.

While the courts have considered the president’s authority under IEEPA, President Trump has demanded that countries commence negotiations with the United States in the hopes of avoiding higher tariff rates for their exporters, claiming in April that his administration would negotiate “90 deals in 90 days.”Footnote ⁷¹ According to the administration, such trade-related agreements would be necessary to eliminate the national emergency concerning the U.S. trade deficit by extracting tariff and non-tariff concessions from these countries.Footnote ⁷² The United States and the United Kingdom announced the reciprocal implementation of certain trade-related guarantees in June.Footnote ⁷³ Shortly thereafter, the administration said that the United States and China agreed to a de-escalation of tariffs and other retaliatory measures, after President Trump had raised tariffs as high as 145 percent on Chinese imports and China had imposed tariffs of up to 125 percent and begun restricting exports on goods like critical minerals.Footnote ⁷⁴ As the administration’s self-imposed deadline of August 1 approached, President Trump also announced that his administration had concluded agreements with the European Union, Indonesia, Japan, the Philippines, South Korea, and Vietnam.Footnote ⁷⁵ At the same time, President Trump announced a new round of “reciprocal” tariffs on a range of other countries.Footnote ⁷⁶ The terms of the deals announced varied based on the country. As of writing, no final agreement text has been made publicly available, negotiations appear to be ongoing with respect to the details, and the nations involved have made sometimes contradictory statements about what has been agreed.Footnote ⁷⁷ Consequently, the status of the “deals” announced thus far as legally binding agreements in any sense is doubtful.

The current U.S. approach to trade agreements raises significant separation of powers concerns. U.S. Trade Representative Jamieson Greer has said that the administration would not seek congressional approval and implementation of the agreements; rather, they would be “negotiate[d] and conclude[d] … as executive agreements.”Footnote ⁷⁸ Ambassador Greer justified this position by asserting that the agreements would include few if any commitments by the United States, and he “[did] not foresee that any U.S. law would need to be changed.”Footnote ⁷⁹ The Office of the U.S. Trade Representative has long argued that trade agreements that do not make changes to U.S. law are within the constitutional authority of the president and not Congress.Footnote ⁸⁰ But the more widely accepted view,Footnote ⁸¹ as reiterated by a bipartisan Congress,Footnote ⁸² is that, regardless of the form of agreement and regardless of whether an agreement requires changes to U.S. law, the executive branch does not have independent power to enter into a trade-related agreement without that authorization. Moreover, these agreements do appear to involve changes to U.S. law that require congressional authorization. Specifically, they contemplate that the United States will raise duties on partner countries permanently, a change that conflicts with trade agreements implemented by statute.Footnote ⁸³

To be sure, Congress has delegated its trade agreement power to the executive in several statutes. Most familiar to the trade policy world is the detailed statutory scheme for FTAs known as Trade Promotion Authority (TPA).Footnote ⁸⁴ Under this framework, the executive can seek expedited legislative approval of an FTA so long as the FTA covers congressionally approved objectives, among other legislative requirements. In addition to TPA, the three-digit tariff authorizations, discussed above, give the president latitude to make agreements to resolve investigations initiated under their terms. Section 301 authorizes the executive branch to enter into an agreement in the context of a Section 301 investigation to eliminate any burden or restriction on U.S. commerce that results from a trading partner’s actions.Footnote ⁸⁵ Section 232 likewise authorizes the president to negotiate an agreement that limits or restricts certain imports.Footnote ⁸⁶ Congress asserted its trade agreement authority recently by approving the Biden administration’s trade agreement with Taiwan after that agreement had been signed.Footnote ⁸⁷ That post hoc legislation was exceptional, although members of Congress have introduced bills that would have a similar effect with respect to the United Kingdom, among other trading partners.Footnote ⁸⁸

Even apart from the separation of powers issues, reaching agreement with the Trump administration presents significant difficulties. First, some trading partners are reluctant to enter into these agreements because they may violate WTO rules.Footnote ⁸⁹ Second, the Trump administration’s decision to violate its own past agreements, including the United States-Mexico-Canada Agreement it negotiated during its first term, has severely undermined the credibility of its promises. Third, although the United States is a party to hundreds of small trade-related agreements,Footnote ⁹⁰ there is no particular template for these tariff-linked agreements, so negotiators lack a model text that could expedite their work. Fourth, given the lack of a template, negotiators have both greater flexibility and greater uncertainty in the substance of their agreements. Already in the U.S.-UK negotiations, the parties have covered considerable regulatory territory beyond tariffs. They have also addressed longstanding non-tariff barriers to their trade relationship, and they have expanded their discussions to cover economic security and “commercial considerations.”Footnote ⁹¹ Other agreements could include commitments to make purchases like the so-called China Phase-One Deal did in 2020, or they could seek to mix and match from other areas of foreign affairs like defense, or debt relief, or they may even include guarantees regarding specific private or private-public transactions.Footnote ⁹² For instance, the administration has touted its arrangement with Japan according to which Japan will invest more than $500 billion in the United States and will purchase $8 billion of U.S. goods.Footnote ⁹³ In the end, these agreements may not resemble modern trade agreements at all. That complexity muddies the relationship between foreign affairs and foreign commerce in an already fraught legal environment.

Over the last several years, the executive branch has sought to take advantage of what some see as blurry lines between international commerce, national security, and foreign policy to defend broad actions by agencies and by the president in international trade. The government was successful in the litigation that challenged President Trump’s first-term trade actions. The president has blurred the lines even further in his second term by invoking IEEPA to institute a major global economic program. The lawfulness of using IEEPA to impose tariffs remains in doubt, as challenges to several of the president’s recent actions wind their way through the courts. For the moment, however, the trade posture of the United States increasingly resembles a vortex of escalating and often unpredictable tariffs, punctuated by occasional informal agreements with particular trading partners.