ROBERT SIEGEL, HOST:
Just a few months ago, few of us had even heard of the group that now calls itself the Islamic State. But now it's preoccupying national governments. Great Britain says the group is one of the greatest security risks to that nation. Today it raised its terrorism threat level. The White House is pushing ahead with plans to combat the group which holds territory across Iraq and Syria. And that could mean launching airstrikes inside Syria. That, as NPR's Carrie Johnson reports, is raising legal questions about how the Obama administration might justify military action.
CARRIE JOHNSON, BYLINE: In the days after 9/11, Congress authorized the White House to use military force - broad authority to strike against al-Qaida. Benjamin Wittes of the Brookings Institution says times are different now.
BENJAMIN WITTES: And the conflict has changed in a very profound set of ways. It's changed geographically. It's changed in terms of the groups that we're fighting.
JOHNSON: For his part, President Barack Obama has notified Congress multiple times since June that he's sending military advisers to Iraq. The White House seems to be relying on a broad legal theory of self-defense to protect Americans from fighters with the group known as the Islamic State. Those fighters overran territory near the U.S. Consulate in northern Iraq. Ashley Deeks teaches national security law at the University of Virginia.
ASHLEY DEEKS: To have a solid self-defense theory, you either have to have already suffered an armed attack by the people you are targeting or you have to think that they pose an imminent threat of armed attack.
JOHNSON: The legal analysis is complicated because now the White House is considering whether to broaden its air campaign to strike targets in Syria. American University law professor Steve Vladeck.
STEVE VLADECK: The longer that the hostilities with ISIS go on the more widespread they become, the less this looks like scattershot incidents of self-defense and the more it looks like the kind of war making that historically and constitutionally usually requires at least some buy-in from Congress.
JOHNSON: And some members of Congress are demanding a say, a call the president says he hears.
PRESIDENT BARACK OBAMA: It is my intention that Congress has to have some buy-in as representatives of the American people, and, by the way, the American people need to hear what that strategy is.
JOHNSON: Benjamin Wittes of Brookings says that's not just the best legal approach, it also makes practical sense.
WITTES: It's not that the president can't do it without Congress. But I do think having some degree of consensus in the form of legislation regarding what we are doing and what we're not doing would be a very healthy thing.
JOHNSON: But with lawmakers positioning for midterm elections in November it's not clear either political party is going to want to vote on military action. That leaves President Obama relying on his constitutional powers as commander-in-chief, powers he promised to limit when he ran for office years ago. Steve Vladeck of American University says the administration may be gun-shy about that approach for political reasons.
VLADECK: Then looks like there actually isn't that much daylight between the very things that candidate Obama was complaining about back in 2008 and the conduct that President Obama seems on the verge of undertaking here in 2014.
JOHNSON: One more reason, Vladeck says, why the White House may be taking its time before making big decisions about military action. Carrie Johnson, NPR News, Washington.
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