President Obama has been emphatically warning Americans about the dangers of a Trump presidency. But these warnings divert attention from a much darker reality. His Justice Department is in fact pushing the law in a direction that will enable the next president to declare war against any “terrorist” group or nation without the consent of Congress.

This reality is clear from the Department’s response to a lawsuit challenging the legality of Obama’s war against the Islamic State.

In 1973, Congress passed the War Powers Resolution over President Richard Nixon’s veto. It represented the culmination of a national effort to prevent future presidents from repeating Nixon’s unilateral escalations in Vietnam. The Resolution provides that, when a president commits American forces to a new military engagement, he has 60 days to gain the explicit authorization of Congress for the war. If Congress refuses its consent, the Resolution requires the commander in chief to withdraw his forces from the battlefield within the next 30 days.

The Resolution represented a fundamental breakthrough. According to Senator Jacob Javits, its leading sponsor:

We live in an age of undeclared war, which has meant Presidential war. Prolonged engagement in an undeclared Presidential war has created a most dangerous imbalance in our Constitutional system of checks and balances. . . . [The bill] is rooted in the words and the spirit of the Constitution. It [aims] to restore the balance which has been upset by the historical enthronement of that power over which the framers of the Constitution regarded as the keystone of the whole Article of Congressional power–the exclusive authority of Congress to declare war; the power to change the nation from a state of peace to a state of war.

In making war against the Islamic State, Obama also launched an assault on the Resolution, attacking Congress's constitutional position as the ultimate arbiter over war and peace. When he began his new military campaign against ISIS in June 2014, he made no effort to gain Congress’s explicit approval within the next 60 days. He asserted that the decade-old Congressional authorizations for President George W. Bush's wars against al-Qaeda and Saddam sufficed for his new war. In doing so, he took advantage of widespread confusion. ISIS did not even exist when Congress authorized Bush’s attacks in 2001 and 2002. And by the time that Obama began his new military adventure, ISIS had become al-Qaeda's bitter enemy.

This is precisely the kind of “undeclared presidential war” that the Resolution aimed to prevent. As Obama’s war moved into its third year, it has generated powerful dissent on Capitol Hill. Its break with the law has led constitutionalists to cross party lines, uniting leaders of the right, left, and center to condemn Obama’s failure to seek Congress’s approval. In the words of Tim Kaine, the senator and Democratic vice-presidential candidate, the war with the Islamic State has “shown to all that neither the Congress nor the president feels obliged to follow the 1973 War Powers Resolution which would cause the president to cease any unilateral military action within 90 days unless Congress votes to approve it.”

But representatives on Capitol Hill can’t go to court to ask the judges to insist that the president follow the law. Under the U.S. Constitution, courts can’t resolve abstract debates between politicians. They only are there to decide concrete “cases and controversies” generated when illegalities do concrete harm to real people.

Here is where Captain Nathan Smith enters into the story. A career officer in the Army, he was ordered to serve a year’s tour of duty in Kuwait at the command headquarters of Operation Inherent Resolve charged with coordinating Obama’s war against ISIS. As an intelligence officer, he was under orders to locate the best sites for military intervention in the ongoing struggle.

Smith believes they violate the express terms of the 1973 statute. Given his oath to “support and defend the Constitution,“ he also believes that he is under an obligation to disobey the illegal orders of his commander in chief when they violate the Resolution and the Constitution. If he follows his oath and disobeys orders, he faces the prospect of a court martial and serious punishment.

To escape this dilemma, Smith filed a lawsuit in federal court in the District of Columbia to get a clear answer on the status of the president’s orders. I am serving as a constitutional consultant in the on-going litigation; my 2015 Atlantic article about the war on ISIS and the War Powers Resolution led Smith to file his lawsuit. Last Thursday, we filed a brief emphasizing the dangers involved in the way the Justice Department has responded to Smith’s lawsuit.

The government is trying to persuade District Judge Caroline Kollar-Kotelly that she should refuse to consider the merits of Smith’s case. It asserts that the Captain lacks the personal stake required to challenge the legality of the war—and ignores the fact that he potentially faces a court-martial if he is obliged to act on his considered legal judgments. Smith is not a conscientious objector. He is a deeply committed career officer who wants to serve his country in the war against ISIS—so long as it is consistent with his oath to “support and defend” the Constitution.

If the Justice Department succeeds in denying Smith a judicial hearing on the merits, this will make it impossible for anybody to appeal to courts to prevent future presidents from treating the War Powers Resolution with impunity. Nobody has a more personal stake in the legality of the war than service members like Smith. If they are denied standing, this will forever preclude all court challenges to presidential war-making.

Our brief elaborates the legal arguments at length. For the larger public, it is more important to emphasize how this Department of Justice maneuver reveals the paradoxical character of Obama’s relationship to Donald Trump. Despite his isolationist tendencies on other issues, Trump has sent ISIS “a simple message … Their days are numbered. I won’t tell them where and I won’t tell them how. We must as, a nation, be more unpredictable. But they’re going to be gone. And soon.” If the Department’s legal gambit succeeds, it will be impossible for anybody to challenge President Trump when he cites Obama’s precedent in taking his battle in “unpredictable” directions.

This is unacceptable. If Trump wins in November, the courts should have precedents to work with that can offer a robust set of defenses against unilateral military adventures. Worse yet, Hillary Clinton herself—in contrast to her running-mate—cannot be relied upon to maintain the integrity of the War Powers Resolution. While she won’t be as erratic as Trump, it is only the serious prospect of judicial intervention that will contain her hawkish inclinations.

Obama should tell the Department of Justice to reverse its position in Smith’s case. Rather than trying to deprive him of a hearing, it should try to convince the court that the war against the Islamic State can be defended on the legal merits.

Even if the Department succeeds on the merits, it will only lead the court to uphold the legality of the present war against the Islamic State. This won’t stop future courts from reining in future presidents when they engage in even more egregious abuses of the War Powers Resolution. In contrast, if the Justice Department continues to block Smith and his future counterparts from the courtroom, Obama is inaugurating an era of unbridled war-making by the commander in chief, without any of the checks and balances contemplated by the American constitutional system.