President Trump’s authority to deport Venezuelan gang members under the Alien Enemies Act is facing skepticism from the federal bench. Mr. Trump has decried a district judge, James Boasberg, as a “Radical Left Lunatic” after he put the president’s deportations on hold. Now a panel of appeals court judges of the District of Columbia Circuit has declined to lift the pause imposed by Judge Boasberg. Does this signal rough seas ahead for Mr. Trump’s plans?

Our advice is against jumping to conclusions. That Mr. Trump has lost in a district court, never mind a politicized one, is not dispositive. Nor is the fact that he lost before a panel of riders of the District of Columbia Appeals Circuit. All sorts of high grade law professors were insisting that the 14th Amendment’s disqualification clause was “self-executing.” The same ilk belittled presidential immunity. Mr. Trump had the last laugh on both.

These columns have explained how the president’s authority to expel foreign nationals under the 226-year-old law was vindicated by the Supreme Court in the case of Ludecke v. Watkins. In that case, an avowed Nazi was expelled by President Truman. In 1948 the high court, by five to four, gave the president wide leeway over how to use the wartime law — even though by the time the Nine ruled, World War II had been concluded.

Today, the president is invoking the Alien Enemies Act in light of what he finds to be “an invasion of and predatory incursion into the United States” by the gang known as Tren de Aragua, which, Mr. Trump avers, has ties to Venezuela’s Maduro regime. The law’s provisions activate during “a declared war,” or when “any invasion or predatory incursion is perpetrated, attempted, or threatened against the territory of the United States.” 

Ay, there’s the rub — at least per the circuit riders. A panel of three judges weighed Mr. Trump’s appeal seeking to lift Judge Boasberg’s hold on the Tren de Aragua deportations. One judge, Karen LeCraft Henderson, was first nominated to the federal bench by President Reagan and later to the appeals court by President George H.W. Bush. Another, Justin Walker, was nominated by Mr. Trump. The third, Patricia Millett, is an Obama nominee.

The panel decided by two to one against lifting Judge Boasberg’s hold. Judge Walker dissented on procedural grounds, but Judges Henderson and Millett cast doubt on Mr. Trump’s ability to wield the Alien Enemies Act. Of the two, Judge Henderson’s appraisal could prove the more concerning to the president’s cause. She allows that the law “vests in the President near-blanket authority to detain and deport any noncitizen” tied to a belligerent state.

Yet Judge Henderson avers that “a central limit to this power” is that America “be at war or under invasion or predatory incursion.” Taking what looks like an originalist approach, Judge Henderson looks at the Act’s text and finds Mr. Trump falls short on proving that America is at war in the law’s sense. A “predatory incursion,” she finds, means “hostilities against the United States by another nation-state.” In short, “Migration alone did not suffice.” 

What, then, of Mr. Trump’s argument that the courts “may not even assess the lawfulness” of the deportations, because it is “a political question unreviewable by the courts”? She says the “suggestion that judicial review of the Alien Enemies Act is categorically foreclosed is incorrect.” She finds that “the legal meaning of war, invasion and predatory incursion — are well within courts’ bailiwick.”

Yet Judge Henderson’s finding appears, at least to green shades, to be crosswise with Justice Felix Frankfurter’s conclusion in Ludecke. Writing for the majority, he found the Alien Enemies Act to be among those laws that “preclude judicial review.” Frankfurter, too, held that the question of whether a war was afoot was a question of “political judgment for which judges have neither technical competence nor official responsibility.”

Judge Millett raises another legal question that could trip up Mr. Trump. She decries his argument that the gang members can be deported without “some semblance of due process to contest the legal and factual bases for removal.” These circuit riders’ holdings, which contrast with Frankfurter’s judicial modesty, could raise the stakes, and the drama, should — and it should — the Alien Enemies Act return to the Supreme Court.