President Obama’s decision to launch airstrikes against ISIS advances in the Kurdish-occupied region in northern Iraq raises the question of the legality of the President’s use of force.

I do not think that the President has to go back to Congress for legal authority to carry out strikes against ISIS. The President’s Commander-in-Chief authority gives him the power to send the military into combat abroad, and Presidents have done so since the beginning of the Republic, a point I made in one of my first law review articles as a professor. For those interested in a fuller treatment, here is a free download of a journal article summarizing the argument and responding to critics, who believe that the Declare War Clause requires Congress to turn its key before the President.

Even if Congress’s declare war power does require the President to get authorization before he can use force, however, the 2002 authorization to use military force against Iraq is still on the books and provides the President with continuing legal support. The AUMF is not just limited to removing Saddam Hussein. It states: “The President is authorized to use the Armed Forces of the United States as he determines to be necessary and appropriate in order to (1) defend the national security of the United States against the continuing threat posed by Iraq; and (2) enforce all relevant United Nations Security Council resolutions regarding Iraq.” I am happy to confess that I had a hand in writing the 2002 AUMF as an attorney in the Justice Department. As an aside, compare our work to that of the Obama Justice Department, which reportedly was asking Congress to repeal the AUMF a few months ago and would have deprived the White House of legal authority for its airstrikes this week!

The disintegration of Iraq and the capture of significant portions of its oil resources, military stockpiles, territory, and population by an al-Qaeda-linked terrorist group poses a serious threat to American national security. In Iraq, ISIS has acquired sophisticated military weapons (included the M-1 Abrams, the most sophisticated battle tank in the world). It will use the country as a recruiting and training ground for every jihadist terrorist in the region. ISIS has declared its intention to attack the United States. Look at what a small group of al Qaeda terrorists were able to do in the 1990s in Afghanistan, which had far fewer resources and population, not to mention a primitive economy.

There are also important U.N. resolutions about maintaining the territorial integrity and political independence of Iraq and ending its threat to regional stability. I outlined those back in 2003 and explained how they worked within the 2002 AUMF. For those interested in a free download, see here. 

The practical limitation on the President’s Commander-in-Chief power is Congress’s power over the purse and its sole right to raise and support the military. Without Congress’s support, President Obama cannot long afford the costs of extended air operations over Iraq. Even in the war against Serbia (which was waged wholly from the air), President Clinton had to go to Congress for more funding. That gives Congress the opportunity to vote to keep hostilities going or to end the operation (by simply doing nothing). Despite the muted complaints of Democratic isolationists and Rand Paul supporters, the majority in Congress (I believe) want the President to be more aggressive in Iraq, not less, and funding should be readily approved. No constitutional conflict will result.