President Donald Trump just declared a national emergency in order to bypass Congress and fund his wall on the southern border.

The president has hinted for several weeks that this option was on the table, but it was never clear if he would actually go through with it, in part because it sets a dangerous precedent and will almost certainly be challenged in the courts.

But the president failed to strike a deal with Democrats that would give him the $5 billion he wanted to build the wall, so here we are. Now there are at least two pressing legal questions: Does Trump have the constitutional authority to do this? And will his declaration survive the challenge it will likely receive in the courts?

I reached out to 11 legal experts and asked them to assess the president’s prospects. The consensus seems to be that while there is enough ambiguity in the law to permit Trump to declare an emergency, his decision to circumvent Congress and use the military to build a wall will very likely lose in court.

Their responses, lightly edited for clarity, are below.

Jessica Levinson, law professor, Loyola Law School

Can President Trump declare a national emergency? Absolutely. Will it get him what he wants? It should not. And it probably will not.

Under the National Emergencies Act of 1976, presidents have broad authority to declare a national emergency. But that is merely the beginning of the inquiry. Once President Trump declares a national emergency, what is the next step? He should point to specific statutory authority to get the resources and funds he needs to build a wall.

There are two statutes that he is most likely to use. One allows the secretary of defense to start a military program if it is needed to support armed forces. The problem here is that there is no real evidence that the armed forces need a wall to support them. Instead, the reverse may be true, you need armed forces to build a wall. The second statute allows the secretary of the Army to direct troops and resources “that are essential to the national defense.” Here, again, we have a problem. There is scant evidence to indicate that a border wall is in fact essential to the national defense.

As in so many of the Trump administration’s policies, we are relying on federal judges to tell us when the president has overreached.

Renato Mariotti, former federal prosecutor, 2007 to 2016, and host of the On Topic podcast

Trump’s emergency declaration is an attempt to circumvent one of the most important constitutional checks on presidential power — the “power of the purse,” to raise and spend money, which is given to Congress under the US Constitution. To do so, Trump will make use of sweeping laws passed by Congress that permit the president to declare a national emergency and for the secretary of the Army to apply funds and personnel to construct “projects that are essential to the national defense” and the secretary of defense to use funds to “undertake military construction projects” necessary to support the use of the armed forces if the emergency requires use of the armed forces.

Although there is strong reason to believe that the situation at the border is not a “national emergency,” the term “emergency” is not defined in the statute, so the focus of a legal challenge will be that our border security does not “require use of the armed forces” and that the construction of a border wall is not “essential to the national defense.”

Our border defense is primarily a civilian, not a military, operation. But the main reason a challenge to this move will likely succeed is that the statutes, as applied to this case, violate the US Constitution. Courts will see what lawmakers in both parties have publicly pointed out — that this action opens the door to presidents spending funds on a variety of non-emergency programs without congressional approval.

Given that our founders believed that it was important to give Congress the power to control how our funds are raised and spent, this challenge will likely be successful.

“The refusal of Congress to fund a presidential vanity project is not an emergency” —Ciara Torres-Spelliscy

Jed Shugerman, law professor, Fordham University

For those wondering about Trump invoking a national emergency: Remember he also ordered [Robert] Mueller’s firing twice (allegedly). His lawyers declined. Trump can’t do any law stuff on his own. How much can Stephen Miller do by himself?

Even then, litigation will run out the clock, even if the plaintiffs challenging the wall don’t ultimately win on the merits. There are many claims that should be valid enough to yield injunctions delaying construction and spending. First, there will be litigation by members of Congress, which will turn on the complexities of standing. Second, if Trump shifts funds from other appropriated projects to the wall, some contractors losing funds arguably have standing to challenge the emergency’s validity. Third, most of the wall would be built on private property, and property owners can challenge the validity of this “public use” under eminent domain.

Even if they lose in the end on the law, it seems likely to me that Trump will run out of time. And I think even the wall’s most ardent supporters understand Trump wasted two years of GOP control of Congress and wasted America’s longest government shutdown to be left with this dead-end backup plan.

Keith Whittington, politics professor, Princeton University

Unfortunately, Trump has a more credible claim than he should to the necessary legal authority to bypass Congress and fund some wall construction, because both Congress and the courts have been very generous to past presidents. Congress has delegated substantial statutory authority to the president to declare emergencies and move already appropriated funds to new military construction projects.

The courts have generally taken a deferential approach to evaluating how the president makes use of such delegated authority and have not required Congress to be more specific. If Congress wants to give the president lots of discretion to do things — including foolish and expensive things — on his own initiative, the courts have been willing to let Congress do that. Just because executive branch lawyers ought to be embarrassed to sign off on border wall construction as a valid use of the president’s national emergency authority does not mean that the courts will actually be willing to say that this does not pass the laugh test.

The good news is that Congress has the power to start clawing back that delegated authority, if the members can actually agree among themselves that leaving Trump with so many legal toys to play with is probably a bad idea. Tying the hands of the president does reduce the government’s flexibility in the case of a genuine emergency, but it would be a good thing if Congress learned to take a more active role in calibrating just how much discretion they want to trust each president with having.

Peter Shane, law professor, Ohio State University

If the president declares a national emergency, his order will have to specify the precise statutory powers he proposes that he or other officers in the executive branch will be exercising in response to that emergency. Judges may be reluctant to second-guess the president in initially issuing the declaration; the National Emergencies Act does not actually provide a definition of “national emergency,” and it might be tough to identify a party so injured just by the issuance of the order that they have standing to sue.

On the other hand, once executive branch agencies start using the statutory authorities the president has designated in his declaration, they will be subject to lawsuits. For example, the Military Construction Codification Act gives the secretary of defense authority in a national emergency “that requires use of the armed forces” to reallocate funds “to undertake military construction projects ... that are necessary to support such use of the armed forces.”

It is not clear, however, whether the armed forces may lawfully be used to build the wall. It is not clear that building the wall is a project “necessary to support” the armed forces building the wall. And it is not clear that the wall would be a military installation of the kind that fits within the statutory definition of “military construction.”

Whether or not the president’s declaration is legal, plaintiffs could directly challenge Defense Department action they would argue is in violation of the Military Construction Codification Act.

Ciara Torres-Spelliscy, law professor, Stetson University

At a moment like this, it may be helpful to go back to first principles, one of which is that America has a president and not a king. Part of being a president and not a king is abiding by the Constitution, which grants the power of the purse to the Congress. President Trump has repeatedly asked Congress (both under unified Republican control and under split Democratic/Republican control) for full funding for his wall at over $5 billion. The Congress said no repeatedly. The refusal of Congress to fund a presidential vanity project is not an emergency.

There are several Supreme Court cases that speak to the limits of presidential power. For example, in Youngstown Steel, President Truman, who was facing a more acute emergency of stoppage of steel production during the Korean War, wanted to seize the steel mills. The Supreme Court rebuffed Truman and told him that even this wartime emergency did not empower him to seize the mills.

And in the Line Item Veto case, the Supreme Court noted that President Clinton could not line-edit legislation. The Court held that the president only had the power to veto or approval full pieces of legislation. What President Trump wants to do with an emergency declaration to reallocate money to his wall seems to fall within these two cases as a constitutionally prohibited act for an American president.

Stephen Legomsky, law professor, Washington University

The purpose of the National Emergency Act was not to authorize presidential declarations of emergency; it was to limit them. The statute, passed in 1976, was specifically designed to curb what Congress saw as excessive and unjustifiable presidential usurpations of congressional powers. The very first sentence begins, “An Act to terminate certain authorities with respect to national emergencies still in effect …” [my emphasis].

This much is crystal clear: There is no national security emergency at the southern border. Illegal entries today are a small fraction of what they were 20 years ago, and the total size of the resulting undocumented population has stayed flat for at least the past 10 years. In contrast, there is indeed a humanitarian crisis, but it’s the one that the Trump administration has unilaterally created through its systematic assault on the right to apply for asylum.

Whether the courts will invalidate the declaration of national emergency is a close question, however. On the one hand, the Supreme Court in Trump v. Hawaii refused to review a presidential claim of a national security threat justifying the Muslim ban. On the other hand, the courts might well fear the implications of a precedent of unquestioning deference to “emergency” declarations. Unlike the fictitious border emergency claimed by President Trump, a future progressive president could make a serious case for a green emergency, a democracy emergency, a gun safety emergency, or a civil rights emergency.

Douglas Spencer, law professor, University of Connecticut

The root of this controversy is the lack of limits on executive power in the Constitution. Article II simply states, “The executive power shall be vested in a President of the United States of America.” The Constitution does not specify what executive power is, or what it permits the president to do. The Constitution does permit Congress to override the president, if it can muster enough votes.

As a general matter, then, courts are very deferential to executive action when it is endorsed by Congress. On the other hand, courts will typically invalidate a president’s actions if Congress has expressly prohibited them. The controversy in this case is that Congress has explicitly delegated authority to the president to declare emergencies. On the other hand, yesterday’s compromise appropriation bill explicitly rejected spending more than $1.375 billion on physical barriers at the border.

As with many of Trump’s challenged actions, the controversy is as much his violation of constitutional norms as it is constitutional rules. This reflects the limits and ambiguity of our constitution as much as the limits of President Trump’s understanding of it. In the specific case of Trump’s emergency declaration, there are strong arguments in favor of deference to the president (even if one disagrees with his premise and his policy goals), and there are strong arguments in favor of limiting the president from end-running the legislative process.

Because there is no clear-cut answer, I would caution against reading too much into lower court rulings on the matter, no matter how they come out. Any judgments will certainly be appealed to the Supreme Court. By that point, Congress may have rendered the issue moot by overriding the president and/or voters may have rendered the issue moot in the 2020 election.

Ric Simmons, law professor, Ohio State University

The short answer is that the president has a non-frivolous claim that he has the power to declare an emergency and use military funds to build a wall under the 1978 National Emergencies Act, but his authority to do so can be challenged on multiple grounds.

The first question is whether there actually is an “emergency” at the southern border. While this designation seems suspect to some, since there has not been any real change in the situation at the border for the past few years or even decades, courts will almost certainly defer to any president who declares an emergency. (In fact, in the dozens of emergencies that presidents have declared under this law, the Supreme Court has never overruled the president and held that an emergency does not exist.)

The second question is that under the Constitution, the Congress has the exclusive right to control spending, so even under a national emergency, the president has to find a statute in which Congress authorizes him to spend this money. 10 USC Sec. 2909 allows the president in case of emergency to undertake military projects that are “necessary to support such use of the armed forces.” It is not clear that the wall is necessary to “support” the military, since the military does not have domestic law enforcement powers to patrol the border against illegal immigration.

33 USC Section 2293 allows the president in case of emergency to divert funds from one project to the other in order to work on an “authorized civil work, military construction, or civil defense project that are essential to the national defense.” The problem here is that the wall is not “authorized” by any law, and furthermore, it is a stretch to say that the project is “essential to the national defense.”

Most reasonable readings of these statutes would come to the conclusion that the president does not have the authority to divert funding to the wall, but once again, the question is how much deference the courts will give to the president in this context.

“This much is crystal clear: There is no national security emergency at the southern border” —Stephen Legomsky

Peter Margulies, law professor, Roger Williams University School of Law

Judging President Trump’s emergency declaration is all about perspective. The law says that the president can take funds from current projects if the situation “requires” the use of US armed forces. The entry of unarmed Central American refugees — many of them women and children — at the southern border doesn’t “require” a military response.

Under US law, immigration control is a law enforcement job performed by ICE and the Border Patrol, not a task for the military. In fact, since it’s a law enforcement job, US law prohibits a direct military role. A lead military role in law enforcement heralds an emerging dictatorship — that’s not a signal that Congress or the framers of our Constitution wished to send.

At the border today, the military is strictly a supporting player, providing ICE with technology or rolling out miles of razor wire. Because the Defense Department views rolling out razor wire as part of military “training,” using our armed forces for such supporting tasks is not illegal. But civilian personnel could perform these tasks just as readily. And while there’s money in the Pentagon budget for training troops, Congress has not budgeted money for a massive public works project like building President Trump’s wall. Congress has budgeted for projects to be built by the Army Corps of Engineers; by declaring an emergency, President Trump would try to use the military’s modest border presence to divert funds from those other needed projects.

But without a clear need for our military, there’s no legal “hook” for Trump’s emergency declaration: The situation at the border “requires” law enforcement, asylum officers, and immigration judges, not soldiers’ purely supporting role. On the other hand, the Supreme Court recently deferred to President Trump on the travel ban and rarely second-guesses the president’s responses on foreign relations.

So a lot turns on whether the Court will see Trump’s emergency declaration as repackaging ordinary law enforcement to get around Congress’s budget limits, or as a legitimate national security move.

Ilya Somin, law professor, George Mason University

This plan is illegal, and would set a dangerous precedent if it succeeds. Article I of the Constitution mandates that “No Money shall be drawn from the Treasury, but in Consequence of Appropriations made by Law.” Only Congress has the power to make such laws. This vital rule ensures no one person can seize control of the nation’s public funds.

To get around Congress, Trump seeks to use emergency powers. Under the poorly structured National Emergencies Act of 1976, Trump may indeed be able to declare an emergency at the border, even though there is no genuine crisis there. But it does not follow that he can therefore appropriate money for the wall. The NEA does not give him unlimited authority, but only a specific set of powers. None of them are broad enough to justify spending money on a border wall.

Some cite 10 USC 2808 and 33 USC 2293 as possible sources of authority. Yet neither grants it. Section 2808 states that if the president declares a “national emergency” that “requires the use of the armed forces,” he can use certain military funds to “undertake military construction projects … that are necessary to support such use of the armed forces.” There is no emergency caused by undocumented immigration that plausibly “requires the use of the armed forces,” nor is a wall “necessary to support such use.” Indeed, the law generally forbids the use of the armed forces for domestic law enforcement, includes immigration enforcement. Section 2293 likewise only applies to a war or emergency that “requires or may require use of the Armed Forces.”

Even if Trump can use an emergency declaration to get the money he wants, that is not enough to build the wall. He also needs the authority to use eminent domain to seize land from numerous unwilling owners. Such authority must be expressly authorized by the legislature; it cannot simply be inferred. And there is no such clear authorization here.

Trump’s attempt to use emergency powers is virtually certain to be challenged in court. While he deserves to lose, it is possible he could prevail, in part because courts often give the president undue deference on immigration and national security issues.

Should he win, it would set a very dangerous precedent. Future presidents, too, could use it to appropriate money and seize private property without congressional authorization, especially if there is some national security pretext for doing so. Conservatives who cheer Trump on today may not be so thrilled when the next Democratic president uses the same sort of power grab to spend money and seize property to promote liberal policies. Americans across the political spectrum have an interest in ensuring that no one person has such sweeping power over our tax money and property rights.