The 1973 War Powers Resolution is what's in question here Poli.
It requires that the President gives 48 hours notice to Congress that he is taking military action, and any action lasting longer then 60 days requires a Congressional vote to continue sustainment.
If he failed to give proper notice under the law - which I'm sure he did - that's one thing. It's quite another to state that we cannot engage in military action without a formal declaration of war. Mind you - Did we sign a peace treaty with Tripoli when last we went to war with them? Or was it just an armistice?
Stand up for what is right, even if you have to stand alone.