[W]hat sanctions exist if the president fails to comply [with the War Powers Act]? Well . . . nothing at all. This isn’t a criminal statute. The remedy remains what it was before the War Powers Act was passed: Impeachment.

Technically, he's right that there's no binding authority to settle this matter. And he's right that the War Powers Act was a constitutionally contested resolution, not a law. But the clear spirit of it is to get the Congress's blessing if a war launched unilaterally by the president is still dragging on after two months. I guess "illegal" is too blanket a term. And the Congress has to initiate action, which neither Republicans nor Democrats want to do, for various cowardly reasons. But that we live in a country where warfare is entirely the prerogative of one man – even in such a marginal case as Libya – remains disturbing. It's about as classic a symptom of an imperial system – over a republican one – that one can find.