Treaties and Executive Agreements

A treaty in the constitutional sense is an agreement the President negotiates and signs, the Senate approves by a two-thirds vote, and the President then ratifies. The Senate may attach reservations or understandings that limit how the United States accepts it. Under the Supremacy Clause, ratified treaties are the supreme law of the land alongside federal statutes, though the Supreme Court held in Medellin v. Texas in 2008 that treaties not designed to take effect on their own require implementing legislation before courts will enforce them.

Most international commitments are not treaties. Congressional-executive agreements are approved by simple majorities of both houses, the route used for trade pacts such as NAFTA, the WTO agreements, and the 2020 United States-Mexico-Canada Agreement. Sole executive agreements rest on the President's own authority, as with the 2015 Paris climate agreement and the 2015 Iran nuclear deal. Since 1789 the United States has concluded more than 1,100 treaties and many thousands of executive agreements, and the Case-Zablocki Act of 1972 requires that Congress be notified of the latter.

Whether a President can withdraw from a treaty without Congress has never been decided by the Supreme Court, which dismissed a challenge to Jimmy Carter's termination of the defense treaty with Taiwan in Goldwater v. Carter in 1979. In practice presidents have withdrawn unilaterally many times. Agreements resting on executive authority alone are easy for a successor to undo, as when the United States left the Paris agreement in 2020, rejoined in 2021, and announced withdrawal again in January 2025. In a 2023 defense law, Congress barred any President from leaving NATO without Senate approval or an act of Congress.