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John K. Veroneau served as deputy U.S. trade representative under President George W. Bush and assistant secretary of defense under President Bill Clinton. He is an adjunct faculty member at the University of Maine School of Law.
The U.S. Supreme Court intends to move quickly to review whether wide-ranging tariffs imposed by President Donald Trump under the International Emergency Economic Powers Act (IEEPA) are lawful. It should decide that they are not.
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The U.S. Constitution provides Congress with the exclusive authority to determine tariff levels. Presidents must rely on statutory authority provided by Congress to raise tariffs because they have no independent power to do so.
And yet, in recent months, Trump has sought to drastically change tariff levels—raising them by more than six times their 2024 levels. Some tariffs have been imposed pursuant to Section 232 of the Trade Expansion Act, which lays out specific criteria and procedures mandated by Congress to institute new levies. But for most new tariffs, particularly those he has deemed “retaliatory,” Trump has relied on IEEPA as the basis of his authority. This law allows the president to take certain actions “to deal with any unusual and extraordinary threat” from outside the United States. For example, IEEPA has been used to block imports from adversaries such as Iran and Russia.
The U.S. Court of International Trade (CIT) ruled in May that while IEEPA grants the president broad authority to respond to international emergencies, the law does not confer “unbounded” power to impose tariffs. The court noted that imposing tariffs is not among the actions expressly allowed under IEEPA. Even if IEEPA could be interpreted to imply such authority, it would be constrained and consistent with other tariff-raising delegations by Congress. The CIT found that using IEEPA in an “unbounded” manner would effectively usurp Congress’s exclusive constitutional authority over tariffs.
The U.S. Court of Appeals for the Federal Circuit affirmed in August the trade court’s ruling that the Trump administration’s so-called emergency tariffs cannot be sustained under IEEPA. Like the CIT, the Federal Circuit reasoned that even if IEEPA could be used in very constrained ways to impose tariffs, it does not permit a president to refashion the entire tariff code.
Affirming the Federal Circuit decision would be consistent with positions and views the justices have expressed in previous Supreme Court cases involving questions of statutory interpretation and separation of powers.
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In Loper Bright Enterprises v. Raimondo (2024), the justices signaled that courts should be less deferential to the executive branch regarding statutory interpretation and should exercise their own judgment. The Federal Circuit in the IEEPA case noted that presidential actions are not subject to the Administrative Procedure Act, a federal law that governs the processes by which federal agencies create and enforce rules. It added, however, that this does not “preclude a court from finding an abuse of discretion regarding the IEEPA substantive boundary.” Because Trump’s expansive reading of his tariff-raising authority under IEEPA is so at odds with Congress’s long-standing tradition of safeguarding its exclusive constitutional prerogatives over tariffs, it warrants little deference.
In West Virginia v. Environmental Protection Agency (2022), the Supreme Court discussed the “major questions” doctrine, which provides that when the executive branch seeks to decide a matter of “vast economic and political significance,” it must have clear authorization from Congress. The economic effect of the IEEPA-based tariffs far exceeds that of other presidential actions found to have run afoul of the major questions doctrine. In response to international emergencies, IEEPA lists various actions a president could take in response—imposing tariffs is not one of them. It is therefore not credible to suggest that Congress “clearly” intended IEEPA to be used by a president to impose tariffs on every good from every country.
Applying the major questions doctrine to foreign-related presidential actions—pursuant to independent authorities under Article II of the Constitution—may be inapt under certain circumstances. But the doctrine is soundly applied when presidents act solely on authority delegated by Congress on matters over which Congress has exclusive control under the Constitution.
In Gundy v. United States (2019), the Supreme Court provided guidance on the non-delegation doctrine, which prohibits Congress from delegating its legislative powers to other branches of government because it would violate the Constitution’s separation of powers principle. Interpreting IEEPA as granting a president unbounded control over tariffs runs afoul of the non-delegation clause. In Gundy, Chief Justice John Roberts joined Justices Neil Gorsuch, Clarence Thomas, and Samuel Alito in expressing particularly strong views in support of non-delegation, reaffirming that legislation cannot provide presidents with “blank checks” to do as they wish.
While courts have been appropriately deferential to presidents on foreign policy matters, such deference is not unlimited. In Zivotosky v. Kerry (2015), the Supreme Court affirmed that “[t]he Executive is not free from the ordinary controls and checks of Congress merely because foreign affairs are at issue.” The major questions doctrine and the non-delegation clause offer such checks.
Tariff-raising authority is not shared by the legislative and executive branches. Congress enjoys this authority exclusively and has defended it vigorously, delegating it to presidents only sparingly under well-defined circumstances and procedures. Trump’s IEEPA tariffs are not imposed according to his constitutional authority under Article II, which could otherwise warrant judicial deference. Rather, he is exercising statutory authority based on a mistaken view that Congress intended IEEPA as a broad delegation of its tariff-setting powers to the president. This claim is unsupportable and merits little deference.
The Court should affirm the Federal Circuit opinion and let Congress decide whether it wishes to set new tariff levels—just as the U.S. Constitution intended.
This work represents the views and opinions solely of the author. The Council on Foreign Relations is an independent, nonpartisan membership organization, think tank, and publisher, and takes no institutional positions on matters of policy.