Jack Goldsmith has an important post discussing how Congress’s appropriation of funding “to combat the real-world threat of the Islamic State of Iraq and the Levant (ISIL)” amounts to an authorization for use of force against ISIL. Read the entire post, for his analysis of how the appropriation overlaps with the War Powers Act, and is consistent with OLC Opinions. The conclusion sums everything up:
I thus think that at from the Executive branch perspective, and probably objectively, Congress is about to vote on an authorization of force against ISIL for at least the duration of this funding. Vote again, I should say, since (as I have explained before) Congress likely authorized the use of force against ISIL when it approved the President’s previous request last year for “Overseas Contingency Operations” funding.
Of course, Congress is not calling its funding an authorization for the use of force against ISIL, much less debating the authorization. But make no mistake: The funding to continue the war against ISIL is an authorization of force against ISIL, albeit a quiet one, designed not to attract attention.