There’s every indication that President Donald Trump and the courts are headed for a constitutional showdown, and only one of them can emerge the victor.

The Trump administration late Saturday urged an appeals court to immediately put on hold a judge’s nationwide order that effectively stopped, albeit temporarily, Trump’s de facto travel ban on all refugees and on immigrants from seven predominantly Muslim countries.

The federal government has begun complying with the order. And as expected, the president has taken to personally attacking the judge, U.S. District Judge James Robart, whom he smeared in a series of Twitter posts that say more about Trump’s apparent disregard for the constitutional order of things than anything else.

But lawyers for the administration are making a more nuanced case in legal filings and at oral arguments in the several courts hearing cases over his executive order ― including in an emergency request seeking to block the ruling Robart issued on Friday. The administration’s argument, if accepted by the courts, is one that could give Trump nearly unfettered power to go even beyond his initial executive order.

The gist of it: Courts should stay out of this altogether, or else national security will be at risk.

In their emergency motion, Department of Justice lawyers told the U.S. Court of Appeals for the 9th Circuit that Robart’s ruling “contravenes the considered judgment of Congress that the President should have the unreviewable authority to suspend the admission of any class of aliens.”

“As the President acted well within both statutory and constitutional authorization,” the filing continues, “the relief irreparably harms our system of government by contravening the Constitution’s separation of powers.”

The view that courts are powerless when the political branches have already laid down the law on immigration is not without legal weight. In another ruling issued Friday, a federal judge in Boston gave the Trump administration its first victory in the flurry of litigation over the travel ban, and declared that it wouldn’t “encroach upon the delicate policy judgment inherent in immigration decisions” by Congress and the president.

Relying on that decision, the Trump administration is taking an even more aggressive stance in the Seattle case, suggesting to the 9th Circuit that Robart’s nationwide order in and of itself could imperil the nation.

“Judicial second-guessing of the President’s national security determination in itself imposes substantial harm on the federal government and the nation at large,” the administration’s brief concluded.

Bob Loeb, an appellate attorney in private practice who for nearly 25 years handled high-profile appeals at DOJ under Republican and Democratic administrations, said claiming that court review itself amounted to “irreparable harm” was beyond the pale.

“I would have never put my name on a filing that said that,” Loeb tweeted.

That’s precisely the tack Trump himself has taken, not just in his angry Twitter tirade against the judge, but in his insistence that the ongoing legal battle over his travel ban is really about the safety of the nation — and not about excluding Muslims, singling out a particular religion or unequal treatment under the Constitution.

“We’ll win. For the safety of the country, we’ll win,” the president told reporters on Saturday. On Sunday, he continued with his attack on the courts.

Just cannot believe a judge would put our country in such peril. If something happens blame him and court system. People pouring in. Bad! — Donald J. Trump (@realDonaldTrump) February 5, 2017

Whether Trump’s mere incantation of national security is something courts must accept at face value will play out in the coming days. But the argument, at least as far as the judiciary is concerned, could be a dangerous slippery slope for the one branch that could serve as a check on Trump’s executive power.

“Until yesterday, pursuant to the Trump order,” wrote Cornell law professor Michael Dorf, “the federal government had been excluding infants and children who need surgery on grounds of national security. If the courts must accept that national security justifies the Trump executive order, we may as well say that there is no more judicial review, because the government will invoke national security in every constitutional case.”