Goldwater v. Carter, 444 U.S. 996 (1979), was a United States Supreme Court case in which the Court dismissed a lawsuit filed by Senator Barry Goldwater and other members of the United States Congress challenging the right of President Jimmy Carter to unilaterally nullify the Sino-American Mutual Defense Treaty, which the United States had signed with the Republic of China, so that relations could instead be established with the People’s Republic of China.
EDIT: I’ve brought it up before because a somewhat-analogous issue was also surprisingly undecided in UK case law, and there was a major legal tussle in the UK over it, whether or not the Prime Minister had the power to withdraw the UK from the EU without going to Parliament.
Actually, whether or not it’s permitted is, surprisingly, an undecided point in case law.
The case law here is Goldwater v. Carter, but the Supreme Court ruled on a technicality rather than the major question.
https://en.wikipedia.org/wiki/Goldwater_v._Carter
EDIT: I’ve brought it up before because a somewhat-analogous issue was also surprisingly undecided in UK case law, and there was a major legal tussle in the UK over it, whether or not the Prime Minister had the power to withdraw the UK from the EU without going to Parliament.