Look to the Constitution.
I would also hope we could agree that the CIC is charged with making war while Congress can fund it or not.
Congress as a body of 535 bloviators is neither equipped nor conducive to making executive decisions which is why I think the CIC has to be given wide latitude in committing troops to combat. Congress can check that power easily but they don't have the balls to do just that.
History tells me that these decisions all become political rather than constitutional questions and I don't see it changing any time soon. And that's probably how it should be.