what can congress do to stop the war?

Congressman (and Presidential candidate) Ron Paul argues, not much other than cutting off funding. In a recent speech before the House of Representatives, Paul discussed why he was voting against a $124 billion supplemental appropriation that also included a weak Congressional mandate about the war in Iraq:

If one is unhappy with our progress in Iraq after four years of war, voting to de-fund the war makes sense. If one is unhappy with the manner in which we went to war, without a constitutional declaration, voting no makes equally good sense.

Voting no also makes the legitimate point that the Constitution does not authorize Congress to direct the management of any military operation – the president clearly enjoys this authority as Commander in Chief.

I find this hard to believe. Is Congressman Paul really saying that once the declaration of war is given, the President has free reign to do anything he wants? I'm not the only one who is skeptical of this position. University of Chicago professor Richard Epstein, in a recent debate, made the following point:

And remember Congress has, and the president does not, an explicit power "to make the rules governing land and naval forces," which is not written in any "narrow fashion." Third, the president has duties that go along with his powers and other functions. Thus "he shall take care that the Laws be faithfully executed," which hardly speaks of vast discretion to choose which to follow and which to disregard.

Looking at all these provisions together, I think that it is possible to answer David's hypotheticals. There is nothing in the text that distinguishes the power of Congress to regulate in peace and in war, but its power "to make Rules for the Government and Regulation of the land and naval Forces" covers both indifferently. If it says that our military forces can only use rubber bullets so be it. But of course it will not, and we don't need to invent some new-fangled presidential power to allow the president to use real weapons in wars.

I have little faith that the current Democratic Congress will do anything meaningful to limit the President, but Epstein makes it clear that it does have the power to do so.