President Obama is considering going it alone, without Congress, without the U.N., and without the British. Per the New York Times:
President Obama is willing to move ahead with a limited military strike on Syria even while allies like Britain are debating whether to join the effort and without an endorsement from the United Nations Security Council, senior administration officials said Thursday.
Although the officials cautioned that Mr. Obama had not made a final decision, all indications suggest that the strike could occur as soon as United Nations inspectors, who are investigating the Aug. 21 attack that killed hundreds of Syrians, leave the country. They are scheduled to depart Damascus, the capital, on Saturday.
The White House is to present its case for military action against Syria to Congressional leaders on Thursday night. Administration officials assert that the intelligence will show that forces loyal to President Bashar al-Assad carried out the chemical weapons attack in the suburbs of Damascus.
The president has previously made much political hay arguing that the executive branch cannot commit troops without Congress and that America must work through the U.N. Obama told the Boston Globe in 2007:
The President does not have power under the Constitution to unilaterally authorize a military attack in a situation that does not involve stopping an actual or imminent threat to the nation.
As Commander-in-Chief, the President does have a duty to protect and defend the United States. In instances of self-defense, the President would be within his constitutional authority to act before advising Congress or seeking its consent. History has shown us time and again, however, that military action is most successful when it is authorized and supported by the Legislative branch. It is always preferable to have the informed consent of Congress prior to any military action.
If the president goes back on his word, the crowds of anti-war protesters — who definitely weren’t just progressives who hated George W. Bush — will presumably take immediately to the streets, papier mâché in tow.