It's over for President Obama's plan to launch a "limited but decisive" strike on Syria. The Washington Post reports, "Prime Minister David Cameron lost a preliminary vote in Parliament late Thursday on intervention in Syria. ... The British parliamentary vote marked a stunning defeat for Cameron’s government."

The Wall Street Journal explains, "Thursday evening's vote was nonbinding, but in practice the rejection of military strikes means Mr. Cameron's hands are tied. In a terse statement to Parliament, Mr. Cameron said it was clear to him that the British people did not want to see military action."

This followed the rejection in the UN Security Council of a resolution authorizing the use of force in Syria; there is no hope that it will ever be passed. "After the council fell short of reaching an agreement, State Department deputy spokeswoman Marie Harf told reporters in Washington that the U.S. sees 'no avenue forward' given Russia's past opposition to action by the council on Syria."

The Obama administration was prepared to go forward without NATO approval either, a sign that it believed support in those quarters was scant as well. Defense One reported that "with its military ready to attack Syria on President Obama’s command, the United States is no longer pursuing a United Nations or NATO stamp of approval to respond with force to the purported deployment of chemical weapons."

Neither has Obama secured the consent of Congress for his planned operation. Speaker John Boehner wrote to the president, saying: "I have conferred with the chairmen of the national security committees who have received initial outreach from senior Administration officials, and while the outreach has been appreciated, it is apparent from the questions above that the outreach has, to date, not reached the level of substantive consultation." Boehner wrote:

I respectfully request that you, as our country’s commander-in-chief, personally make the case to the American people and Congress for how potential military action will secure American national security interests, preserve America’s credibility, deter the future use of chemical weapons, and, critically, be a part of our broader policy and strategy. In addition, it is essential you address on what basis any use of force would be legally justified and how the justification comports with the exclusive authority of Congressional authorization under Article I of the Constitution.

Jack Goldsmith, the Henry L. Shattuck Professor at Harvard Law School, examines the legal authority under which presidents can order a military action without the authorization of Congress. He noted that the previous presidents invoked treaty obligations and national interest considerations notably absent in this case.

What is the important national interest in intervening in Syria? No U.S. persons or property are at stake. That fact alone distinguishes most executive branch precedents. In the Libya opinion, OLC argued that the “credibility and effectiveness” of a Security Council Resolution gives rise to an important national security interest. This is a stretch considered by itself – but in any event, there is no Security Council resolution for Syria. Nor can OLC even invoke the “credibility and effectiveness” of a regional organization in which the USG participates (such as NATO, in Kosovo) as giving rise to an important interest that would justify the President’s use of military force. That leaves the weakest of all interests: preservation of “regional stability” and maintenance of “peace and stability.” These interests will of course always be present when the President is considering intervention, and thus by themselves are no limit on presidential power at all. Such interests were invoked in Libya and in earlier OLC opinions, but they were always invoked in connection with other factors (such as the consent of the nation in question) or other interests (such as the protection of U.S. persons or property, or the preservation of the U.N. Charter or a regional security treaty commitment), and never as sufficient by themselves.

Now, with Britain out of the operation, Obama faces the prospect of going into Syria almost literally alone, without the UN, NATO, Congress, or even the UK to back him up. Two courses are now open to him. He can climb down as best he can and pretend he's changed his mind or he can go forward risking a wider war for nothing. As Andy Borowitz of The New Yorker said in a satirical piece, Obama has tried to mollify the antiwar left by promising the Syria strike "would have no objective." It would just be a couple of days worth of random drive-by shooting without strategic content and therefore moral.

Yet a climbdown would represent a public and devastating humiliation of the man who once believe he bestrode the world. It would also represent a huge propaganda victory for Assad.

The alternative would be for Obama to double down and order an attack on his own authority despite having, as Professor Goldsmith noted, no apparent legal leg to stand on. He would risk starting a wider war that he doesn't even want to win, and possibly illegally to boot.