The biggest casualty in the struggle against the Islamic State so far has been the American Constitution. One year into the battle, the president and Congress threaten to destroy all serious restraints against open-ended war-making by the commander-in-chief. President Obama waited for half a year before even submitting a draft resolution authorizing his initiative. But it is now obvious that the Republican-controlled Congress finds it politically convenient to stand on the sidelines and let Obama take the blame for the escalating instability. That leaves only the Supreme Court to halt this transformation of the president into a latter-day King George III.

As The Atlantic’s Garrett Epps rightly emphasizes,  allowing the president to go unchallenged will produce a terrible precedent. As the rise and rise of Donald Trump suggests, future presidents may make aggressive use of their powers as commander in chief—and they will predictably point to Obama’s unilateral war on ISIS to justify their own military adventures.

Enter the Supreme Court. Since the justices would deny standing to the bipartisan group of legislators on Capitol Hill who have failed to convince their colleagues to take their constitutional responsibilities seriously, everybody has assumed that the Court will remain on the sidelines as Obama’s war continues. This is a mistake.

Existing case-law establishes that individual soldiers can go to court if they are ordered into a combat zone to fight a war that they believe is unconstitutional. During the closing years of the Vietnam War, two federal courts of appeal carefully considered, and unanimously affirmed, the standing of soldiers to bring such complaints. Neither court backed those challenges on the merits, but the facts surrounding Richard Nixon’s escalation in Vietnam raised very different issues from those raised by the ISIS campaign.

The Supreme Court never resolved the standing question in the 1970s. But the case law allows a single brave soldier to bring the issue before today’s justices. How should they answer it?

The Court has wisely left it to the political branches to work out their inter-branch conflicts over foreign policy. But the decision over war and peace is special. The Constitution explicitly requires the president to gain congressional approval. This founding commitment was reinforced by the passage of the War Powers Resolution, over Richard Nixon’s veto, in 1973. Responding to the popular movement against Nixon’s Vietnam escalations, Congress established clear ground-rules for the future. Henceforth, presidents would be required to gain explicit Congressional consent within 60 days of initiating “hostilities,” and if they failed, they had to withdraw from the battle within the next 30 days.

Obama claims these requirements don’t apply to his war. In his view, the old resolutions President Bush obtained against Al Qaeda and Saddam Hussein in 2001 and 2003 supply the requisite Congressional consent for his campaign. That holds true, the administration argues, even though according to General Martin Dempsey, chairman of the Joint Chiefs of Staff, the battle  will continue through 2018.

Most lawyers and scholars, myself included, have criticized this effort to use decade-old resolutions as the basis for a war against a terrorist group that didn’t even exist when Congress authorized the invasions of Afghanistan and Iraq. But even if the Roberts Court upheld the administration’s view, it would put future presidents on notice that the justices will seriously scrutinize further efforts to transform the resolutions of 2001 and 2003 into open-ended grants for new military adventures.

The Supreme Court’s emergence from the sidelines could only proceed with deliberate speed. When confronting an order into the zone of conflict, a member of the military must first have the courage to raise a legal challenge. It would then take a year or more before the case could make it to the Supreme Court. During this interval, the threat of judicial intervention might persuade key actors on Capitol Hill to pass a resolution defining the war’s aims and limits. But if it doesn’t, Congress’s continued passivity will make it clear that the Court is the only remaining check on presidential adventurism.

Decisive judicial intervention would not lead to a head-on confrontation with the White House. The Court would simply rule that Mr. Obama has misconstrued the War Powers Resolution, and that the sitting president—probably Obama’s successor—must obtain Congressional approval if he wants to continue hostilities after the 60-day deadline. This would force the issue to the top of the legislative agenda, and require all sides to hammer out the terms of battle for the next commander-in-chief—redeeming  the Founders’ vision for a new century.