So, a simple majority of both houses is all that's required? No Presidential signature required? That sounds like a legislative veto to me. Is that unconstitutional?
@Maj. Bill Martin
A one-house legislative veto was struck down decades ago in
INS v. Chadha. Whether or not they'd strike down the two-house resolution in the WPA is unknown. Legal opinions go both ways. The best argument against it is that it's not something that appears anywhere in the Constitution, and limits Presidential authority. The argument for keeping it in Chadha was basically "it's necessary in some cases."
The WPA has references to a "joint resolution", that seemingly would require a Presidential signature, but also a "concurrent resolution" of the two chambers, which would not. So at bottom, the WPA authorizes the two chambers of Congress to force the removal of U.S. troops from a conflict without a Presidential signature. That's in Section 5(c) of the WPA.