The Constitution gives Congress the power to declare war. Congress has not formally declared one since 1942. It has nevertheless developed an extensive modern practice for voting on wars already in progress.
On June 23, the Senate voted 50–48 to approve a House-passed concurrent resolution directing the president to remove United States forces from unauthorized hostilities with Iran. The measure was not presented to the president and was widely described as nonbinding.
The following day, the chamber considered whether to proceed to a joint resolution addressing the same hostilities. A joint resolution could become law if approved by both chambers and signed by the president, or enacted over a veto. The motion failed, 47–50.
The two votes established a stable arrangement. The Senate approved the instruction that could not compel the executive branch and blocked the version that could enter the statutory process. Opposition was recorded. Authority remained where it was.
The arrangement was tested again Thursday. The House passed another Iran war-powers resolution, 214–208. The Senate rejected a similar measure, 47–49. Congress had therefore supplied both constitutional functions in a single afternoon: one chamber applied the check, and the other supplied the balance.
Checks and balances are ordinarily described as friction between branches of government. That design requires multiple institutions and may take time. The Senate's refinement produces the same friction internally, allowing the chamber to oppose a war, decline to bind it and return to opposing it without assistance from the executive branch.
“The resolutions concern the same conflict. The vote totals are public. The outcomes differ according to what each measure could do.”Dr. Eleanor March, Institute of Applied Coincidences
March declined to classify the sequence as contradictory, noting that contradiction requires two positions while the Senate had maintained one position through several outcomes.
The conclusion is procedural rather than partisan. Congress's war power has become the power to hold votes about war. The votes have sponsors, roll calls, reconsiderations and a permanent place in the Congressional Record. The military operation continues outside that record, leaving each institution free to perform the part assigned to it.
The last formal declaration of war named foreign governments. The modern resolution names hostilities and directs their removal. If the direction does not produce removal, Congress retains the direction and may vote on it again.