What is the War Powers Act?

It is an act of congress passed after the Vietnam War, over President Nixon's veto, and of dubious constitutionality, which seeks to define and limit the powers of the president of the United States to command the armed forces. The most important provision is that if the U.S. armed forces go into combat the president must get a resolution from congress authorizing the mission. If the resolution is not passed then the forces must be withdrawn from the combat within sixty days. Since it was passed no president has ever acknowledged its validity but, nonetheless, have complied with it.