Yesterday, Scott Lemieux wrote about President Obama's executive war powers overreach, and why it's become so typical:
Surprisingly, it's not that the president has systematically ignored or overridden Congress. In fact, the presidency has become the dominant war-making power precisely because this is how a majority of legislators want it. The president initiated major wars in Korea, Vietnam, and Iraq (twice), and in all of these cases -- sometimes before the fact, sometimes after -- Congress has passed the buck, delegating to the president the power to authorize force rather than declaring war itself. Senators and congressmen and women are similarly happy to pass on the blame when things go bad. Hillary Clinton's assertion that her vote for the 2002 authorization for President George W. Bush to use force in Iraq was not an authorization for the preemptive war Bush actually fought is an instructive illustration of how Congress tries to have it both ways.
Now, if you argued that there's no way that Congress' abdication of its constitutional responsibilities lets the administration off the hook for ignoring its own, you'd still be right. But how committed is Congress to avoiding the issue? So committed the Senate just voted down Sen. Rand Paul's attempt to clarify the president's authority using Obama's own 2007 statements about when the executive can act without congressional authorization by 90-10.
Paul's amendment was an obvious attempt to make Obama look bad, but since when have Republicans shied away from doing that? They really just don't want to constrain the ability of the president to wage war unilaterally.