On an amendment offered by Senator Robert Dole (R-Kansas) to the Foreign Military Sales Act, the Senate votes 81 to 10 to repeal the Tonkin Gulf Resolution. In August 1964, after North Vietnamese torpedo boats attacked U.S. destroyers (in what became known as the Tonkin Gulf incident), President Johnson asked Congress for a resolution authorizing the president “to take all necessary measures” to defend Southeast Asia. Subsequently, Congress passed Public Law 88-408, which became known as the Tonkin Gulf Resolution, giving the president the power to take whatever actions he deemed necessary, including “the use of armed force.” The resolution passed 82 to 2 in the Senate, where Wayne K. Morse (D-Oregon) and Ernest Gruening (D-Alaska) were the only dissenting votes; the bill passed unanimously in the House of Representatives. President Johnson signed it into law on August 10. It became the legal basis for every presidential action taken by the Johnson administration during its conduct of the war.

Despite the initial support for the resolution, it became increasingly controversial as Johnson used it to increase U.S. commitment to the war in Vietnam. Repealing the resolution was meant as an attempt to limit presidential war powers. The Nixon administration took a neutral stance on the vote, denying that it relied on the Tonkin resolution as the basis for its war-making authority in Southeast Asia. The administration asserted that it primarily drew on the constitutional authority of the president as commander-in-chief to protect the lives of U.S. military forces in justifying its actions and policies in prosecuting the war.