The gulf of tonkin resolution was repealed in 1970 because?

In 1970 the administration began to shift its stance. It asserted that its conduct of operations in Southeast Asia was based not on the resolution but was a constitutional exercise of the President's authority, as Commander in Chief of U.S. military forces, to take necessary steps to protect American troops as they were gradually withdrawn(the U.S. had begun withdrawing its forces from Vietnam in 1969 under a policy known as "Vietnamization"). Mounting public opinion against the war eventually led to the repeal of the resolution, which was attached to the Foreign Military Sales Act that Nixon signed in January 1971.