Rep. Justin Amash (R-Mich.). (J. Scott Applewhite/AP)

It would be illegal for the White House to launch a military strike against Syria without congressional approval, Rep. Justin Amash (R-Mich.), one of the most outspoken GOP critics of President Obama and congressional leaders, said Tuesday.

The Michigan lawmaker used his Twitter account to respond to the news that House Speaker John A. Boehner (R-Ohio) has been consulted by the Obama administration about the potential use of force against Syria. Amash said that if Boehner believes the president will use force, the speaker should call the House back to Washington to debate and vote on that decision:


In a separate Twitter message, Amash said it is "unquestionably unconstitutional & illegal" for the president to strike Syria without congressional authority. He added a link to The War Powers Act, which requires the president to notify Congress when troops are ordered into areas where "imminent" hostilities are likely. Under the law, troops must be withdrawn within 60 days unless Congress formally declares war.

Amash is one of 13 GOP co-sponsors of a bill that would restrict any funding for U.S. military operations in Syria without prior congressional approval. The list of co-sponsors includes some of the most conservative lawmakers in the Republican-controlled House.

But they are not alone in calling on the White House to seek congressional approval for military action. In a statement Monday, Sen. Tim Kaine (D-Va.) said he is pleased to hear that the administration is consulting lawmakers about potential military options. "Absent an imminent threat to United States national security, the U.S. should not be engaged in military action without Congressional approval," he added.

Jackie Kucinich contributed to this report.

Follow Ed O'Keefe on Twitter: @edatpost