In an editorial, the New York Times says: Capt. Nathan Michael Smith, who is 28, is helping wage war on the Islamic State as an Army intelligence officer deployed in Kuwait. He is no conscientious objector. Yet he sued President Obama last week, making a persuasive case that the military campaign is illegal unless Congress explicitly authorizes it.

“When President Obama ordered airstrikes in Iraq in August 2014 and in Syria in September 2014, I was ready for action,” he wrote in a statement attached to the lawsuit. “In my opinion, the operation is justified both militarily and morally.” But as his suit makes clear, that does not make it legal.

Constitutional experts and some members of Congress have also challenged the Obama administration’s thin legal rationale for using military force in Iraq and Syria. The Federal District Court for the District of Columbia should allow the suit to move forward to force the White House and Congress to confront an important question both have irresponsibly skirted.

The 1973 War Powers Resolution requires that the president obtain “specific statutory authorization” soon after sending troops to war. Mr. Obama’s war against the Islamic State, also known as ISIS and ISIL, was billed as a short-term humanitarian intervention when it began in August 2014. The president and senior administration officials repeatedly asserted that the United States would not be dragged back into a Middle East quagmire. The mission, they vowed, would not involve “troops on the ground.” Yet the Pentagon now has more than 4,000 troops in Iraq and 300 in Syria. Last week’s combat death of a member of the Navy SEALs, Special Warfare Operator First Class Charles Keating IV, underscored that the conflict has escalated, drawing American troops to the front lines.

“We keep saying it’s supposed to be advising that we’re doing, and yet we’re losing one kid at a time,” Phyllis Holmes, Petty Officer Keating’s grandmother, told The Times.

Asked on Thursday about the lawsuit, the White House press secretary, Josh Earnest, said it raised “legitimate questions for every American to be asking.” The administration has repeatedly urged Congress to pass a war authorization for the war against the Islamic State. It currently relies on the authorization for the use of military force passed in 2001 for the explicit purpose of targeting the perpetrators of the Sept. 11 attacks, which paved the way for the invasion of Afghanistan.

“One thing is abundantly clear: Our men and women in uniform and our coalition partners are on the front lines of our war against ISIL, while Congress has remained on the sidelines,” the White House spokesman Ned Price said in an email.

Yet, the White House has enabled Congress to shirk its responsibility by arguing that a new war authorization would be ideal but not necessary. Administration officials could have forced Congress to act by declaring that it could not rely indefinitely on the Afghanistan war authorization and giving lawmakers a deadline to pass a new law.

By failing to pass a new one, Congress and the administration are setting a dangerous precedent that the next president may be tempted to abuse. That is particularly worrisome given the bellicose temperament of Donald Trump, the likely Republican nominee.

It is not too late to act before the presidential election in November. The Senate majority leader, Mitch McConnell, and House Speaker Paul Ryan have shown little interest in passing an authorization. They should feel compelled to heed the call of a young deployed soldier who is asking them to do their job.