Can Obama strike Syria without Congress' consent?

President Obama has yet to say what course of action he'll take to respond to the alleged use of chemical weapons by President Bashar al Assad's regime in Syria, but his administration has previewed the justification it will use if Mr. Obama decides to take military action.

Mr. Obama on Wednesday said he has "no interest in any open-ended conflict in Syria." However, he added, "we do have to make sure that when countries break international norms on weapons like chemical weapons that could threaten us, that they are held accountable."

To launch an assault against the Assad regime that meets domestic legal standards, Mr. Obama's actions would have to pass constitutional muster and meet the statutory requirements set by the 1973 War Powers Resolution.

Before taking over the executive branch, Mr. Obama and Vice President Joe Biden strongly asserted that the president's ability to use military force is constrained by Congress. Yet since Mr. Obama took over the White House, the administration hasn't shied away from unilaterally deciding to take limited military action.

Mr. Obama's approach follows one that presidents have taken since the end of World War II, when administrations started exercising their war powers more independently. Some administrations have argued the War Powers Resolution is unconstitutional, but the Supreme Court has never weighed in on the issue -- leaving the extent of the president's war powers an open question.

"Part of the problem is these are legal issues, and legal issues are settled in court at the end of the day," James Lindsay, a senior vice president at the Council on Foreign Relations, told "And when courts choose not to adjudicate it, people are free to lay down their interpretation of the rules."

Predictably, when it comes to war powers, the president has the political advantage -- he is, after all the commander in chief. Congress, however, has the constitutional authority to declare war, so legislators do their best to keep the president's powers in check.

As a senator and presidential candidate in 2007, Mr. Obama said, "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. In instances of self-defense, the president would be within his constitutional authority to act before advising Congress or seeking its consent."

Biden, also a senator and presidential candidate in 2007, said he would move to impeach President Bush if he unilaterally attacked Iran because of its nuclear programs.

In 1998, Biden said on the Senate floor, "To be sure, the commander in chief ensures that the president has the sole power to direct U.S. military forces in combat. But that power - except in very few limited instances - derives totally from congressional authority."

Yet in 2011, the administration took military action in Libya without any congressional approval, prompting the Republican-led House of Representatives to vote to rebuke the president.

In its legal justification for action in Libya, the Justice Department's Office of Legal Counsel (OLC) argued that Congress' authority to declare "war" was limited by the definition of war. "This standard generally will be satisfied only by prolonged and substantial military engagements, typically involving exposure of U.S. military personnel to significant risk over a substantial period," the OLC wrote.