The Obama administration is considering several legal theories to justify an expanded military campaign against the Islamic State [“Obama weighs military action,” front page, Aug. 23]. The “range of options” under discussion is said to include “temporary authority under the War Powers Resolution, constitutional authority for emergency action to protect U.S. citizens” and new congressional authorization. Only the last of these options satisfies the Constitution.

It is a common misconception that the 1973 War Powers Resolution allows the president to use force for 60 days without prior congressional approval. In fact, the War Powers Resolution says the opposite:

“Nothing in this [law] . . . is intended to alter the constitutional authority of the Congress or of the President” or “shall be construed as granting any authority to the President with respect to the introduction of United States Armed Forces into hostilities . . . which authority he would not have had in the absence of this” law.

Save for a few narrow exceptions — none of which permits all of the current combat mission in Iraq, much less a broader one — the constitutional rule is that the president can lawfully use military force only if Congress first authorizes it, not that the president may do so until Congress stops it.

Scott Roehm, Washington

The writer is senior counsel for the Constitution