Legislation was written to give the President the authority to combat terrorists.

The Authorization for the Use of Military (AUMF) in 2001 was unveiled as a response to the terror attacks. It stated “that the President is authorized to use all necessary and appropriate force against those nations, organizations, or persons he determines planned, authorized, committed, or aided the terrorist attacks that occurred on September 11, 2001, or harbored such organizations or persons, in order to prevent any future acts of international terrorism against the United States by such nations, organizations or persons.”

On Nov. 13, 2001, President George Bush signed a military order to detain non-US citizen enemy combatants and try them under military tribunals.

Soon after, the AUMF was expanded in 2002, to “legalize” the preemptive war in Iraq. The propaganda basis for the preemptive strike was that Iraq harbored terrorists, had weapons of mass destruction, and was hostile to the U.S.

http://blog.tenthamendmentcenter.com/2012/11/guantanamo-forever-indefinite-detention-indefinitely/

2012: Obama passes NDAA