That would be akin to Congress listening to President Bush's address on the Iraq war last year and then killing the authorizing resolution.
And if Bush went ahead and still went to war, what would Congress do?
If they felt it to be an act of a tyrant, they would impeach him.
Bills fail all the time, many times due to wording the Congress does not like, not direct opposition to the bill's intent.
Impeachment, not refusal of bills is how Congress deals with tyranny.
But only after the war had started, with no prior authorizing resolution, and passing a bill later than demands witdrawl of the US from Iraq.