Sure, they can attempt to deny funding for it.
Let them try.
There, the lesson in basic Constitutionalism is over. For now.
Exactly.
SEC. 3. AUTHORIZATION FOR USE OF UNITED STATES ARMED FORCES.
(a) Authorization.--The President is authorized to use the Armed Forces of the United States as he determines to be necessary and appropriate in order to--
(1) defend the national security of the United States against the continuing threat posed by Iraq; and
(2) enforce all relevant United Nations Security Council resolutions regarding Iraq.