Enacted over President Nixon’s veto in November 1973, the War Powers Act (Resolution) of 1973 required that “in every possible instance” the President must consult with Congress before sending troops into hostilities.
The law also required that, when the President commits forces, he must send a full explanation to Congress within two days. He must withdraw forces within sixty days unless Congress expressly gives him permission to keep them in battle. In reality, the act gives the President the power to wage war for sixty days without congressional approval.
Congress hoped the law could prevent future Vietnams. Actually, though, it reflected the political weakness of the presidency in the 1970s. Nixon saw the act as unconstitutional. So have all his successors, Democrat or Republican.
Photograph by John Sonderman (Flickr)