Former CIA director John Brennan testifies on Capitol Hill in May 2017 before the House Russia investigation task force. (Pablo Martinez Monsivais/AP)

Former CIA director John Brennan said Sunday that he’s considering “going to court” to challenge President Trump’s decision to strip him of his security clearance. If he does, plenty of lawyers with expertise in security clearance cases stand ready to help him.

“There’s a ton of us who would do it pro bono,” Mark Zaid, one of the nation’s leading litigators in the field, told The Washington Post on Sunday night.

“I’d be privileged to have him as a client,” said R. Scott Oswald, who specializes in defending whistleblowers at the Employment Law Group.

But none of the attorneys interviewed by The Washington Post in the wake of Brennan’s comments were confident that Brennan, or any of the other officials and former officials threatened by Trump, would prevail in the end.

The deference the courts have traditionally shown the president in matters of national security presents a formidable obstacle, they said, citing in particular a 1988 ruling by the Supreme Court in Department of the Navy v. Egan, in which the justices said, in Zaid’s words, that judges “don’t have the expertise” to adjudicate clearances and “should not be trying to insert” themselves in the process.

Charles McCullough III, a partner in the Compass Rose Legal Group and former inspector general for the Office of the Director of National Intelligence, called the prospects in court “quite slim.”

But that doesn’t mean there won’t be battles.

“If there’s ever a case that would represent an exception,” Oswald said, “it’s this one.”

After “the president told us what was on his mind” in his interview with the Wall Street Journal, where he stated that he was aiming at “these people who led” the Russia probe, Oswald said, Trump essentially acknowledged that his motivations were “totally political.”

Plus, if Brennan chooses to challenge Trump’s action, he could stir up quite a fuss, presenting the president with yet another continuing struggle on top of all the others he’s facing. And it could be a long one, Zaid said, lasting years.

That’s because the process is nowhere near as simple as Trump made it sound when he said in a letter read by press secretary Sarah Huckabee Sanders on Thursday that he had “exercised my constitutional authority to deny Mr. Brennan access to classified information.”

In fact, Trump’s letter appears not to have actually formally revoked anything. Rather, the president said he would “direct appropriate staff of the National Security Council to make the necessary arrangements with the appropriate agencies to implement this determination.”

Meanwhile, Brennan said Sunday he hadn’t been contacted by anyone in government, only by lawyers offering help and “former colleagues and friends expressing their support. . . . To me, that’s not surprising at all, the way this White House” works, he said on NBC’s “Meet the Press.”

Indeed, specialist lawyers interviewed by The Post weren’t even sure entirely sure what had transpired.

“I’m not sure that what the president meant was to actually use the word ‘revocation,’ ” Zaid said, referring to Brennan’s security clearance eligibility.

“I’m not sure whether his clearance was actually ‘revoked,’ ” McCullough said. “That is a critical question. It may have just been deemed to have expired in view of his retirement.”

It’s conceivable, the lawyers noted, that Brennan could be denied access to classified information while still remaining “eligible” for access, that is, technically holding onto his security clearance but simply not allowed to see or hear anything of a classified nature.

“Right now,” Oswald said, “we don’t have anything formalized that describes the reason for the revocation. And importantly, the executive order requires that.”

The executive order to which he referred was promulgated by President Bill Clinton and later amended in 2008. It sets out a process that, if followed by the administration, could take years to play out, Zaid said.

It requires, with a major escape hatch to be sure, that those facing revocation shall be provided, among other things:

A “comprehensive and detailed . . . written explanation” of the decision.

Notice of their right to be represented by a lawyer at their own expense.

The chance to request “any documents” and reports . . . “upon which a denial or revocation is based.”

A “reasonable opportunity to reply in writing, and request a review” of the decision.

A right to appeal to a “high level panel” appointed by the head of the relevant agency, presumably the CIA in Brennan’s case.

An opportunity “to appear personally” and present materials before “an adjudicative or other authority.”

The same process would apply to all those threatened by Trump with security clearance revocation if indeed the president followed through.

But “Trump is unlikely to go down this path because it affords far too much due process for his taste,” as Bradley P. Moss, a partner in Zaid’s firm, wrote in Lawfare in July.

“It would require civil servants at the respective agencies [of those losing their clearances] to sign off on the paperwork. I can say with a reasonable degree of confidence,” Moss wrote, “that those civil servants would not put their names on a document moving to revoke someone’s security clearance for nothing other than bad-mouthing the president on television or writing a book.”

Rather, Moss suggested, the administration would be more likely to invoke a “national security” exception in the executive order that eliminates the appeal process. But, Moss wrote, this would require “current agency heads” to sign off on a bypass of due process. And some might not consent.

Trump would then have to claim the “inherent constitutional authority” to revoke the clearances.

That, he wrote, “has never happened before.”

“If the president were to take this unprecedented exercise of his authority . . . it would set up a serious clash of constitutional questions,” Moss wrote, with an unforeseeable response from the courts.

“As the president would say, we’ll just have to wait and see.”