President Barack Obama faces a familiar question as he contemplates airstrikes in Syria: Should Congress have a say in his decision? Obama was barreling toward strikes last summer when he abruptly announced that he first wanted approval from congressional lawmakers.
But Congress balked at Obama's request for a vote and the operation was eventually scrapped. This time around, the White House is suggesting it may not be necessary to get a sign-off from Congress for airstrikes.
While cautioning that Obama has made no final decisions, officials say there is a difference between last year's effort to attack Syria's government in retaliation for chemical weapons use and a bombing campaign against Islamic State militants that is now under consideration.
"What we're talking about now is confronting a terrorist group that has sought safe haven in Syria," White House spokesman Josh Earnest said when asked about the prospect of Obama again seeking congressional authorisation.
"This is a group that poses a threat to Americans in the region and could potentially, down the line, pose a broader threat to American interests and our allies around the globe."
Earlier this month, Obama authorised US airstrikes against Islamic State targets in Iraq. The militants have been moving with ease between Iraq and Syria, effectively blurring the border between the neighboring nations.
Thus far, there has been little clamor among congressional leaders for Obama to seek approval from Capitol Hill before proceeding with military action in Syria. And with the midterm elections just over two months away, lawmakers may be even less inclined to take a politically risky vote on military action.
"I see no reason to come to Congress because, if he does, it'll just become a circus," Democratic Rep. Steve Cohen, said this week.
Still, there are notable members of both parties who are calling for a vote if Obama seeks to move into Syria. Republican Sen. Bob Corker, a frequent critic of the administration's foreign policy, has said Congress should "certainly" authorise any military action in Syria.
Sen. Tim Kaine, a Democrat and White House ally, has also called for a vote on the president's broader strategy for going after the Islamic State group "I am calling for the mission and objectives for this current significant military action against ISIL to be made clear to Congress, the American people, and our men and women in uniform," said Kaine, using one of the acronyms for the militant group. "Congress should vote up or down on it."
Obama's surprise decision on Syria last year underscores the degree to which the dynamics in Washington could quickly flip. The president could ultimately decide to seek congressional approval once again, and more lawmakers could demand that he take that step.
Legal experts say Obama would have the authority to launch airstrikes in Syria without congressional approval, though they say his standing would be strengthened if the scope and duration of the attacks were limited.
"The Constitution gives only Congress the power to initiate war," said Ilya Somin, a law professor at George Mason University. "You could argue that a small number of strikes over a small number of days does not constitute a war."
Obama authorised the ongoing strikes in Iraq without congressional approval. The White House offered a trio of justifications for the unilateral action: an imminent threat to American personnel stationed in Iraq, a request for assistance in countering the militants from the Iraqi government and a humanitarian crisis in northern Iraq, where militants had trapped religious minorities.
The military launched three more airstrikes in Iraq on Wednesday, bringing the total number of US strikes to 101 since August 8.
Defense officials say the US is also considering a humanitarian relief operation for Shiite Turkmen in northern Iraq who have been under siege by militants for weeks. While Obama initially resisted going after the Islamic State group in its operating base in Syria, his calculus appears to have shifted after the militants announced that they had killed American journalist James Foley.
The group is threatening to kill other US hostages, including journalist Steven Sotloff, whose mother released a video Wednesday pleading with the captors to release him.
Extending airstrikes into Syria would also require compliance with international law. The clearest basis for military action would be a UN Security Council resolution.
However, Obama is unlikely to get that authorisation, given that Russia, the biggest benefactor of Syrian President Bashar Assad, would probably wield its veto power unless military action were coordinated with the Syrian government.
Some international law experts argue that airstrikes could be justified as a matter of self-defense. Obama could argue that the Islamic State group poses a threat to the US and its allies from inside Syria, whose government is unwilling or unable to stop it.
Anthony Clark Arend, a government and foreign service professor at Georgetown University, said Obama could also argue that he was acting alongside Iraq in the interest of "collective defense."
That theory would posit that the strikes in Syria are an extension of Iraq's request to the US to help it fight the Islamic State group.
Another possibility: Although the US has said it will not coordinate with Assad, the Syrian dictator could give secret, back-channel consent to American attacks.
The US has a similar arrangement with the Pakistani military for US drone strikes there, even though Pakistani officials publicly condemn the American actions.