"In December 1978, President Carter decided to recognize the People’s Republic of China, instead of the Republic of China, simultaneously invoking the termination clause of the Mutual Defense Treaty with Taiwan. Senator Goldwater and other members of the Senate and House sued, contending that termination could not be constitutionally effective without concurrence of the entire Congress. D.C. District Judge Oliver Gasch enjoined the Secretary of State from taking action to implement the termination, holding that the U.S. could not terminate the Treaty until the President’s actions received the approval of two-thirds of the Senate or a majority of both Houses of Congress. President Carter appealed contending that the case presented a non-justiciable political question that should not be resolved in the courts but rather through give-and-take accommodation of the political process. The D.C. Circuit reversed on the merits, concluding that the President had not exceeded his constitutional authority; no judge would have declined to exercise jurisdiction by reason of the political question doctrine. The Supreme Court reversed without argument and ordered the case dismissed, with a plurality concluding that the case was non-justiciable under the political question doctrine.."
http://legalhistoryblog.blogspot.com/2018/02/from-goldwater-to-zivotofsky-political.html
"While dismissing the case of Goldwater v. Carter, the Supreme Court left the question of the constitutionality of the President Carter's action open. Powell and Rehnquist merely questioned the judicial merit of the case itself; they did not explicitly approve Carter's action.[9] Moreover, Powell even stated that this could be a valid constitutional issue.[2] Article II, Section II of the Constitution merely states that the President cannot make treaties without a Senate majority two-thirds vote. As it stands now, there is no official ruling on whether the President has the power to break a treaty without the approval of Congress."
https://en.wikipedia.org/wiki/Goldwater_v._Carter
So, what if Goldwater had prevailed in the Supreme Court in *Goldwater v. Carter*? Could Carter get congressional approval of the termination of the US-RoC mutual defense treaty, and if not, how would that affect US-PRC relations? There is also the question of the broader implications of ending a president's power to unilaterally terminate treaties, e.g. George W. Bush's decision to withdraw from the ABM treaty. (And of course there's Trump and the Paris agreement on climate and the Iran nuclear deal
https://en.wikipedia.org/wiki/Joint_Comprehensive_Plan_of_Action but the Obama administration's position was that these were not treaties and did not require Senate ratification. Indeed, the tendency of nations to reach agreements by things other than formal treaties would presumably reduce the impact of a Supreme Court decision in Goldwater's favor...)