President Trump walks out of the White House to speak about border security on Jan. 4. (Jabin Botsford/The Washington Post)

Harry Litman teaches constitutional law at the University of California at San Diego and practices law at the firm Constantine Cannon. He was U.S. attorney for the Western District of Pennsylvania from 1998 to 2001 and deputy assistant attorney general from 1993 to 1998.

Even as President Trump prepares to address the nation Tuesday night on his cherished wall, his advisers are still trying to determine whether he should invoke his emergency powers to push the project through. If Trump chooses the emergency route, he will be launching a high-stakes legal battle whose conclusion is uncertain.

On the one hand, the move offers the president a possible face-saving escape from a tough situation — really, a “win” for the president — permitting him to declare victory on a long-promised initiative and end the political battle, which he appears to be losing, over shutting down the government.

But a rebuke from the courts — where Trump’s batting average is already low — would be a clear humiliation. And the courts will take up the issue fully understanding that Trump’s claims of an emergency rest on lies. There is, in fact, no emergency. There are only desperate would-be immigrants who pose virtually no threat to the national security of the county.

What makes the decision such high political drama is that Trump has decent legal arguments on his side — not always the case with this administration. Here is the basic legal landscape:

In 1952, the Supreme Court reviewed President Harry S. Truman’s emergency takeover of the nation’s steel mills to put an end to a strike that Truman argued threatened ongoing steel production during the Korean War. The court held that neither the Constitution nor Congress had provided him the authority to close the mills.

In a canonical concurring opinion in that case, Justice Robert H. Jackson set out a governing framework for assertions of emergency power. He found that the question turned on whether Congress had (1) authorized the assertion of power (in which case presidential authority is at “high ebb”), (2) taken no action (the authority falls in a “zone of twilight”), or (3) opposed it (presidential power at “low ebb”).

That opinion remains the leading precedent on a president’s declaration of emergency powers. It suggests that if the court finds that Congress has authorized emergency powers that cover the building of Trump’s wall, he will prevail. But if it finds that Congress has rejected it, he will lose.

Fast-forward to 1976, when Congress, looking to curb promiscuous assertions of presidential emergency powers, passed the National Emergencies Act, which requires presidents to specify which powers they intend to use. It further holds that a declared state of emergency sunsets unless the president renews it annually.

In practice, however, the law has proved a boon to presidential power. It appears to give the president unfettered discretion to announce an emergency, and presidents have routinely renewed these annually. More important, Congress has never attempted to exercise its powers to end an emergency. The upshot is that about 30 states of emergency remain in effect today, each of which provides access to dozens of statutory provisions.

Can Trump add one more, by fiat, in his address to the nation Tuesday night? Probably. Certainly, any other president would have broad running room under the National Emergencies Act to do just that.

The second part of the White House’s submission would be that, having declared an emergency, he has access to the various statutory provisions. The White House would likely invoke two that speak to “military construction activities” to support or protect the safety of U.S. troops. Each is a stretch.

The pivotal legal question is likely to be whether the courts defer to Trump’s determination as president or whether they review it independently. Will the question be framed as “is there an emergency?” or “Did the president plausibly conclude that there is an emergency?”?

On the all-important question of deference, there is an elephant in the room that the courts no doubt see. Trump is an inveterate liar, and his assertion of an emergency is grounded in a flurry of shifting falsehoods: Illegal border crossings are down, not up. Terrorists are not coming in to the country at the southern border. Former presidents do not support building the wall.

In fact, the New York Times has reported that the whole idea of the wall came from Trump advisers Roger Stone and Sam Nunberg as a way to try to keep their erratic candidate on message about immigration generally. It’s hard to imagine a less credible genesis for a state of national emergency.

This gives a court skeptical of Trump’s probity two bites at the apple. It could hold either that there is no emergency — Trump’s claims notwithstanding — or that the specific powers that Trump is attempting to harness to build the wall cannot be stretched to that purpose. It would then enter an injunction suspending the efforts to build the wall while the issue works its way through the courts, a process that would be expedited but that still would require a few months at least.

And yet. The court — and especially the Supreme Court — will surely also be sensitive to the potential consequences of calling the president a liar, as deserved and obvious as it may be here. That is because it could commit the court to a regime of second-guessing presidential declarations, hamstringing genuinely necessary emergency powers. Might the justices let him proceed so as not to clip the wings, in a genuine emergency, of the other, more honest presidents to come?

Trump’s hope has to be that the court judges not him but his office.

Read more:

Jennifer Rubin: An ‘emergency’ power grab would only add to Trump’s problems

Henry Olsen: Trump is threatening to go around Congress to get his wall. History shows he’ll fail.

John Q. Barrett: How Congress can stop Trump’s ‘emergency’

Greg Sargent: The real national emergency is the threat of Trump’s collapse

Alexandra Petri: I am declaring a state of emergency