Article Two of the United States Constitution
The Constitution does not say how the United States can end a treaty.  Since the Constitution has passed, the government has done this in a few ways.  In 1798, the first time the government wanted to end a treaty (the 1778 Treaty of Alliance with France), Congress passed a law ending the treaty. Other times, in the 1800s, a few Presidents ended treaties after Congress asked them to. The first time a President ended a treaty without Congress's approval was in the 1970s, when President Jimmy Carter ended a treaty with the Republic of China.  In a lawsuit called Goldwater v. Carter, members of Congress asked the Supreme Court to clarify whether a President could end a treaty on his own.  The Supreme Court could not agree on a decision, and the case was dismissed (ended without a decision).