PRESIDENT OBAMA is going before Congress to request authorization for the limited use of military force in a battle of up to three years against the Islamic State. On the surface, this looks like a welcome recognition of Congress’s ultimate authority in matters of war and peace. But unless the resolution put forward by the White House is amended, it will have the opposite effect. Congressional support will amount to the ringing endorsement of unlimited presidential war making.

Whatever else they decide, the House and Senate should revise the White House initiative to guarantee that it won’t have this tragic result. First do no harm; before proceeding with a debate over the limits of our continuing military engagement, Congress should make it impossible for future presidents to evade its final decision.

The problem is the double-barreled position advanced by Mr. Obama. He asserts that he already has sufficient congressional authority for an open-ended war with the Islamic State, also known as ISIL or ISIS. He bases this claim on an expansive reading of Congress’s 2001 resolution authorizing President George W. Bush to make war on Al Qaeda after the 9/11 attacks. As long as this resolution remains on the books, Mr. Obama claims, he can continue fighting, even if Congress never agrees to a new resolution.

For political cover, Mr. Obama now wants Congress to grant him new authority, and yet he opposes repeal of the 2001 authorization in exchange for that new authority. Although he has pledged to refine, and ultimately repeal, the old resolution, he has failed to follow through on similar commitments in the past. If Congress contents itself with another empty promise, it is highly likely that the old act will remain on the books when the new resolution runs out in 2018. This will allow Mr. Obama’s successor to reassert his current position and continue fighting on the basis of the authority he inherited from the Bush era.