The Bush administration's plan to build a missile-defense site in Alaska appears to be a first step toward the United States abrogating or withdrawing from the 1972 Anti-Ballistic Missile Treaty. (Last year, Explainer described the difference between withdrawing from the ABM Treaty and abrogating it.) Can the president break treaties? Can Congress stop him?
As a practical matter, the answers are "yes" and "not really," though it's not well-established in constitutional law. Article II, Section 2 of the Constitution declares that the president "shall have Power, by and with the Advice and Consent of the Senate, to make Treaties, provided two thirds of the Senators present concur." But it doesn't say anything about the power to break treaties.
The United States last withdrew from a treaty in 1979, when President Jimmy Carter unilaterally terminated the Mutual Defense Treaty with Taiwan in order to recognize the mainland Chinese government. Sen. Barry Goldwater, R-Ariz., and 20 other senators sued, arguing that if you need two-thirds of the Senate to make a treaty, breaking one also requires a two-thirds majority. The Supreme Court dismissed Goldwater's complaint, but because it was a plurality decision, no binding precedent was set. (Click here to read the Supreme Court's decision in Goldwater vs. Carter.)
Senators who support the ABM Treaty could sue Bush for withdrawing, but will they? Probably not, because the current court is unlikely to be amenable to their argument, and the senators wouldn't want to run the risk of eliciting a decision that expanded presidential power.
Congress could bar the government from spending money on the Alaska missile-defense site. But that wouldn't affect the status of the ABM Treaty--Bush could withdraw from it anyway. Besides, no such bill is in the works, Bush would veto it in any event, and the current Congress would never override his veto.
Bonus Explainer: Despite what everyone thinks, the Senate doesn't ratify treaties. Technically, the president ratifies a treaty after two-thirds of the Senate consents. Theoretically, the Senate could consent to a treaty, and the president could refuse to ratify it. But as a political matter, that's unlikely to happen.
Explainer thanks James M. Lindsay, senior fellow at the Brookings Institution, and Slate reader Dan Eggers for asking the question.