Nearly five months after launching a war against the Islamic State, in Iraq and Syria, the Obama administration has gotten around to requesting formal authorization from Congress to conduct that war.

While indefensibly late, the move is nonetheless welcome if it triggers the long-needed substantive debate about the goals, scope and justification of a military intervention that was launched with the claim of authority from laws passed more than a decade ago to allow the use of force in Afghanistan and Iraq.

In seeking a three-year authorization, President Obama appears to be trying to avoid leaving an open-ended mandate that his successor could interpret unjustifiably broadly, much as his administration has. The request sets limits on the use of ground forces, which is good news if Congress and the White House view that as explicitly ruling out another protracted intervention.

The parameters of a proposed war authorization the White House sent to Congress on Wednesday, however, are alarmingly broad. It does not limit the battlefield to Syria and Iraq, the strongholds of the Islamic State, also known as ISIS or ISIL, which is attempting to form a caliphate. It also seeks permission to attack “associated persons or forces” of the brutal group, a term that appears to be excessively expansive and could undermine Mr. Obama’s stated intent to limit the force authorization.

While a new Authorization for Use of Military Force, or A.U.M.F., would sunset the 2002 law Congress passed to pave the way for the invasion of Iraq, it would leave intact the 2001 mandate for the war in Afghanistan. That is problematic, considering that the Obama administration has relied on that law to start attacks that were well beyond the scope of what lawmakers authorized at the time. In a letter to Congress delivered on Wednesday, Mr. Obama reiterated his intent to “refine, and ultimately repeal” that statute, which serves as a foundation for American military operations in Afghanistan. He should go further and set a date for its expiration.

If the White House prevails, it would get virtually unrestricted power to engage in attacks around the globe as long as it can justify a connection, however tenuous, to the Islamic State.