“Just as the U.S. has conducted operations against terrorists elsewhere, there is no legal reason preventing you from targeting ISIL in Syria,” Rubio wrote in a letter sent to the president Friday, using an alternate acronym for the group.

Rubio’s position is at odds with Sen. Rand Paul (R-Ky.), another potential GOP presidential candidate.

Paul too has said he supports expanding airstrikes to Syria, but chastised the president for circumventing the Constitution by not debating military action through Congress.

Speaker John Boehner (R-Ohio) and others have said it is “questionable” whether the president has the authority to target the group in Syria.