John Yoo quoted by Washington Examiner, April 12, 2018
“I think that statutory authorization comes from the [authorization for use of military force] passed after 9/11, which allows the use of force with regard to any group connected to the 9/11 attacks, which includes ISIS (which is an offshoot of al Qaida). Because ISIS is operating in Syria, the U.S. can use force in Syria,” Yoo said in an email.