The Pentagon’s top commander in the Middle East told Congress today that Iraq’s self-defense gives the United States a legal justification to intervene in next-door Syria.

US Central Command chief Joseph Votel told the House Armed Services Committee that the 2001 Authorization for Use of Military Force (AUMF), signed by President George W. Bush to go after the plotters of the Sept. 11, 2001, terrorist attacks, remains in effect for the US fight against the Islamic State (IS) in Syria. As US troops hunt down some 2,000 remaining IS fighters in the Euphrates River Valley, the legal core of the US involvement in Syria derives from Iraq’s defense, he said.

“Our legal basis for operating in Syria was largely driven by the collective self-defense of Iraq,” Votel told Rep. Tulsi Gabbard, D-Hawaii, who stoked controversy by visiting Syrian President Bashar al-Assad last year. “While we were beginning to address [IS] in Iraq, we knew that we also had to address [IS] in Syria.”

“We saw the rise of [IS] and the inability of Iraqi Security Forces to address it as it was growing,” Votel said of the impact of US troops' departing Iraq in 2011. Syria’s inability to deal with the IS threat in turn has jeopardized “a much broader group of countries around the world,” he said, including US partners in Jordan, Lebanon and Turkey.