I’m no constitutional lawyer, not even a lawyer at all, but it seems quite clear that the involvement of the US in ‘supporting’ NATO’s military action in Libya qualifies as ‘hostilities’. Short of news articles explaining Obama’s decisions and his legal argument to justify the US’s involvement as not being hostilities, I have failed to see a single commentary that suggests otherwise.
I can understand why it may be politically expedient for Obama to classify the involvement as not being hostilities, thereby removing the need to get approval from Congress. It certainly makes life a lot easier for Obama and removes any fear that the US will not be able to fulfill it’s commitment and be forced to stop it’s involvement.
That said, I think Obama ought nevertheless to go through the normal procedures with Congress. Certainly, there are dissenting voices in both the House and Senate that oppose the war, but I don’t see any real likelihood that he would loose the vote or funding. As it stands, Congress and the media seem more riled up about Congress being circumnavigated than by the US’s involvement in the conflict itself. So it seems unlikely that Congress would vote to significantly defund the operation. At the same time, it removes a purely (so far) political issue that makes Obama look more and more like Bush and less and less like the candidate he once was.
Bruce Ackerman, a professor of law and political science at Yale, takes on the legal aspect of the issue quite nicely in his Op-ed for the New York Times. I think it’s worth the read: http://www.nytimes.com/2011/06/21/opinion/21Ackerman.html