The Supreme Court today delivered a landmark 6-3 ruling that President Trump does not have the authority to impose sweeping tariffs under the International Emergency Economic Powers Act (IEEPA) — vindicating warnings that UCLA Law's Kimberly Clausing had been sounding for months. Professor Clausing is available to speak with journalists about the ruling’s legal, economic, and geopolitical implications.

Chief Justice John Roberts, writing for the majority, held that the President must identify “clear congressional authorization” to exercise broad tariff authority — and concluded that no such authorization exists under IEEPA. The cases before the Court — Learning Resources v. Trump and V.O.S. Selections v. United States — marked the first time a challenge to a Trump second-term policy received a full Supreme Court hearing.

Why Prof. Clausing Saw This Coming

In December 2025 testimony before the House Ways and Means Committee, Professor Clausing addressed the legal underpinnings of the tariff regime directly:

“Normally, tax increases are enacted by Congress, which is clearly given authority over all taxes (including tariffs) in the US Constitution (Article 1, Section 8). While Congress has delegated some narrow authority over tariffs to the President with limited exceptions, the majority of current tariff revenue comes from tariffs that rely on the International Emergency Economic Powers Act (IEEPA). For reasons extensively covered in recent Supreme Court briefs, nearly all observers agree that the President’s use of tariffs exceeds IEEPA authority... Congress should assert control over its power of the purse, including tariff authority.”

Her testimony also anticipated the economic stakes of today’s ruling, providing one of the most comprehensive pre-ruling analyses of the tariffs’ impact on consumers, businesses, and workers.

“Trump Administration tariffs are the largest tax increase on American consumers in a generation, lowering standards of living for all Americans while generating both economic disruption and a deterioration of US standing in the world,” Prof. Clausing in testimony before the US House Ways and Means Committee

About Professor Clausing

Professor Clausing holds the Eric M. Zolt Chair in Tax Law and Policy at UCLA Law and previously served as Deputy Assistant Secretary for Tax Analysis at the U.S. Department of the Treasury, where she was the lead economist in the Office of Tax Policy during the early Biden Administration.

She is the author of Open: The Progressive Case for Free Trade, Immigration, and Global Capital (Harvard University Press, 2019) and has testified before the House Ways and Means Committee, the Senate Committee on Finance, the Senate Committee on the Budget, and the Joint Economic Committee.

To arrange an interview with Professor Clausing, please contact her by writing 
clausing@law.ucla.edu or media@law.ucla.edu

Additional UCLA Law Experts

UCLA School of Law faculty are available to comment on a wide range of international and domestic legal issues shaping the current political landscape, including international law and the law of armed conflict, presidential and executive power, foreign relations law, election regulation, constitutional law, and federal–state relations.

Media Contacts: media@law.ucla.edu

Carl Marziali carl@lindavistapr.com 

Geoffrey Baum geoff@lindavistapr.com