As expected, Donald Trump’s “national emergency” is headed to court: Four major lawsuits have so far been filed challenging the emergency declaration and seeking to enjoin construction of the border wall.

Can any of them stop him?

The leading cases are California v. Trump, filed on behalf of 16 mostly blue states; Sierra Club v. Trump, filed by the ACLU; El Paso County v. Trump, filed by a group founded by Obama administration officials called the Protect Democracy Project; Alvarez v. Trump, filed by the Audubon Society and Public Citizen.

While the parties and venues for the cases differ, three leading arguments have emerged, based on the Constitution’s separation of powers, the statutes on which the Trump administration relied for its declaration, and environmental law.

First, each suit argues, in various ways, that the emergency declaration violates the Constitution’s separation of powers, in particular the Appropriations Clause that (Article I, Section 9) which provides that “No Money shall be drawn from the Treasury, but in Consequence of Appropriations made by Law.”

Trump’s action obviously violates this clause, unless the Constitution’s broad grant of executive power (and the National Emergency Act, which governs the use of that power) carves out an exception—which is what courts, and ultimately the Supreme Court, will have to decide.

In addition, the Sierra Club case adds a citation to the relatively obscure Presentment Clause of the Constitution. (Article I, Section 7). That clause spells out the procedure for presidential vetoes; the ACLU’s argument is that if Trump wanted more money for the border wall, his constitutional avenue would have been to veto the $1.4 billion appropriation. But since he didn’t do so, he agreed to be bound by its terms.

“ To file a lawsuit, parties must show that they are individually harmed by the action at issue. In a controversy like this one, obviously the main conflict is political, but that’s not the same as a judiciable matter for courts. ”

Second, all four cases argue that Trump’s actions were ultra vires, a legal term meaning “beyond the powers” granted to him by the statutes he relied upon.

In making his emergency declaration, Trump relied on four statutes: the National Emergency Act; the Military Construction Codification Act, which provides that the military may undertake military construction projects in the event of a national emergency; the Support for Counterdrug Activities Act, which empowers the military to assist in anti-drug activities; and the Treasury Forfeiture Fund.

In varying ways, the plaintiffs in the four lawsuits argue that Trump’s actions go beyond the authority conveyed by these four statutes. Given the factual evidence, this is not an “emergency” as the NEA defines it, and there is no justification for the military spending. California v. Trump is the most dramatic in this part, providing reams of data that show there is no border security crisis, no evidence of a terrorist threat, and no evidence (and plenty of contrary evidence) that a wall would help with preventing crime or drug trafficking.

All of the cases also argue that Trump’s actions violate the Appropriations Act of 2019, which allocated $1.4 billion, and no more than that, for border barrier construction. Since Congress specifically set an amount to spend, the lawsuits argue that Trump has no authority to exceed that amount.

Finally, three of the four cases argue that the border wall construction violates the National Environmental Policy Act (NEPA), which requires environmental impact statements for all significant government actions. That may sound like a footnote in a case as contentious as this one, but it’s also the strongest single statutory hook.

Given the similarity in legal bases, which case has the best chance of success?

It’ probably the most prominent of the emergency lawsuits is California v. Trump, filed by California’s enterprising attorney general Xavier Becerra. (The last person to hold Becerra’s job was Kamala Harris.) Filed in the Northern District of California–part of Trump’s least favorite judicial circuit, the Ninth Circuit–the case probably has the highest profile of the four.

On the other hand, one issue that distinguishes the cases from one another is the matter of standing. To file a lawsuit, parties must show that they are individually harmed by the action at issue. In a controversy like this one, obviously the main conflict is political, but that’s not the same as a judiciable matter for courts.

In the California case, the states argue that they are harmed by the diversion of resources to the border wall. But because of Trump’s recourse to military budgets, that’s actually a hard argument to make; it’s not clear that the money for the wall is being diverted from money that would otherwise be spent in New York or Massachusetts.

Sierra Club is also filed in the Northern District of California, and could well be consolidated with California v. Trump. But unlike the 16 states, the Sierra Club and a group called the Southern Border Communities Coalition, specifically allege the kind of injury that is common in environmental cases. Some of this is almost comical: members of the coalition enjoy hiking in the area, and their hikes will be spoiled if the border wall is built. Likewise in Alvarez, some residents are complaining that their property values will go down.

Obviously, these are not really the main reasons anyone opposes a flimsy national emergency to build an unnecessary border wall. But they are the kind of “injuries” that are often necessary to get into court in the first place.

For that reason, Sierra Club may be a safer case in procedural terms.

Then there are questions of venue.

El Paso County v. Trump is distinguished mostly by its venue; unlike Sierra Club and California, it was filed in the Western District of Texas, which is part of the Fifth Circuit. Unlike the Ninth Circuit, the Fifth Circuit has a reputation for being conservative, and is growing more so under Trump. It’s possible that if El Paso County makes it to the Supreme Court, the Court will review a more conservatively written lower court opinion.

Alvarez v. Trump, meanwhile, has been filed in the D.C. District Court. Its claims are similar to those of the other cases, and the groups behind it are less prominent than the ACLU or the State of California. But it is possible that Alvarez could be decided before the other cases and get to the Supreme Court first.

At this stage, it’s too soon to tell, but the two non-California cases are, in a sense, hedging their bets rather than placing all their faith in a single judicial venue.

Finally, an ancillary case has been filed by the left-leaning Citizens for Responsibility and Ethics in Washington, or CREW. CREW’s lawsuit is focused not on the alleged constitutional violations but on the lack of transparency in Trump’s decision-making process. Specifically, neither the Department of Justice nor the White House provided any documentation outlining the president’s legal authority to declare a national emergency in this case, despite requests from CREW that they do so.

Such documentation is important, of course, because it ordinary lays out the legal rationale for a particular executive action. Here, perhaps tellingly, nothing whatsoever has been provided.

While the array of cases can seem dizzying, it’s not unusual for multiple lawsuits to be filed in high-profile controversies. After Trump’s travel ban was declared, for example, nearly 50 cases were filed in federal court; Trump v. Hawaii was ultimately the one decided by the Supreme Court, in large part due to the various revisions of the ban, the timing of the different cases, and the injunction that a lower court judge in the case had placed on the ban.

The challenges to the border wall are similar. While the best legal arguments have now been made by some of the sharpest legal minds in the country, which plaintiffs make it to the Supreme Court is often a matter of luck.