Is Congress rediscovering its role in shaping — or constraining — the use of American military force? The House has now passed, and the Senate seems likely to pass, a resolution prohibiting the president from taking action against Iran without explicit congressional authorization, except in the case of imminent threats. This resolution is, in a narrow sense, a response to the Donald Trump administration's decision to kill the Iranian military commander Qassem Soleimani without meaningfully consulting Congress in advance. Yet it also reveals that the United States may be reaching an inflection point in its post-9/11 approach to the use of force.

It is worth remembering how we got here. After the terrorist attacks of Sept. 11, 2001, Congress gave President George W. Bush significant, but hardly unlimited, leeway in responding. Legislators rejected a White House proposal that would have authorized Bush to take action to prevent any suspected terrorist attacks — by any group — against the U.S. They instead focused the legislation on those organizations and state sponsors that had played a role in 9/11. This 2001 Authorization for the Use of Military Force was then complemented by a 2002 measure that covered operations to disarm and ultimately overthrow Saddam Hussein in Iraq.

Supporters of the 2001 legislation — which passed overwhelmingly — could not have expected that it would be used, two decades later, to justify military operations across large swaths of Africa and the Middle East. After 9/11, however, the relatively long leash Congress had given the president grew ever longer, for geopolitical and political reasons.