Last Friday, President Donald Trump declared a national state of emergency at the southern border, adding that it wasn’t one of those emergencies he actually “needed” to declare and then saying a bunch of other things. As he predicted, a coalition of 16 states filed a federal lawsuit on Monday night, seeking a preliminary injunction to prevent the president from acting on his emergency declaration. As he also predicted, that suit was filed in federal district court in California.

What Trump did not predict—and probably could not, given his tenuous grasp on the legal limitations of executive authority—is that Monday’s lawsuit is, at bottom, extremely conservative. The suit does not appeal to the justices’ empathy for vulnerable immigrants or question whether Trump’s racist motives might undermine the declaration’s legality. Instead, it relies upon ancient principles of separation of powers to make a very strong case that Trump has short-circuited the Constitution. It is not a lawsuit about equality, or dignity, but about the nuts and bolts that undergird the constitutional lawmaking process. It is wonky, and formal, terse, and unromantic. And if the Supreme Court’s conservatives have any consistency, Monday’s lawsuit should persuade them to block Trump’s wall.

The 16 plaintiff states center their 57-page complaint around a basic argument: that the president has violated the cardinal principle of separation of powers by trammeling Congress’ will to achieve his policy preferences. Trump, the lawsuit alleges, “has used the pretext of a manufactured ‘crisis’ of unlawful immigration to declare a national emergency and redirect federal dollars appropriated for drug interdiction, military construction, and law enforcement initiatives toward building a wall on the United States-Mexico border.” There is “no objective basis” for this declaration, as Trump himself has essentially admitted. Further, “[t]he federal government’s own data prove there is no national emergency at the southern border that warrants construction of a wall,” and unauthorized entries are “near 45-year lows.”

Much of the complaint details funding that will be diverted from National Guard and drug-interception projects favored by the states in order to build the wall instead. The plaintiffs say that grants them standing to sue in federal court since the president is redirecting money that would benefit their interests to a project that will not. But the states aren’t simply upset because they would have preferred that the money be used for military construction and law enforcement. They are upset because, they allege, the money has been taken from these projects and from their citizens to be used illegally.

Trump, the plaintiff states write, has “violated the United States Constitution’s separation of powers doctrine by taking executive action to fund a border wall for which Congress has refused to appropriate funding.” By “unilaterally diverting funding that Congress already appropriated for other purposes to fund a border wall for which Congress has provided no appropriations,” the president has run afoul of the Presentment Clause.

These problems ought to be catnip for SCOTUS ’ conservative justices.

This lawsuit joins a series of others that have already been filed by watchdog groups. While they all argue that there is no actual emergency at the southern border, that is not the gravamen of their complaint. Instead of asking the courts to second-guess Trump’s intent, these challengers ask them to decide whether Trump had authority to act in the first place.

The answer, they assert, is no. The Presentment Clause is straightforward: For a bill to become law, it must pass both houses of Congress, then be presented to the president for approval. Yet Congress never passed a bill authorizing and funding the border wall Trump now demands. It never presented such legislation to the president for his signature. This is the stuff of Civics 101. Whatever powers the National Emergencies Act may grant to the president, a federal statute cannot override the Constitution. The executive cannot use funds Congress did not appropriate. He cannot amend statutes himself to create money for pet projects. Trump asked Congress for a large sum of money to construct a border wall; Congress resoundingly and provably said no. The National Emergencies Act does not give him leeway to contravene Congress’ commands.

These problems ought to be catnip for SCOTUS’ conservative justices—particularly Justice Neil Gorsuch. In his very first dissent on the Supreme Court, Gorsuch extolled the virtues of this pristine constitutional system. “If a statute needs repair,” he wrote, “there’s a constitutionally prescribed way to do it. It’s called legislation.” Gorsuch continued:

To be sure, the demands of bicameralism and presentment are real and the process can be protracted. But the difficulty of making new laws isn’t some bug in the constitutional design: it’s the point of the design, the better to preserve liberty.

A year later, in his rightly celebrated opinion in Sessions v. Dimaya, Gorsuch hammered this same point home again. “Under the Constitution,” he wrote, “the adoption of new laws restricting liberty is supposed to be a hard business, the product of an open and public debate among a large and diverse number of elected representatives.” The courts abdicate their responsibility when they ignore the Constitution’s “division of duties” between the branches of government. These “structural worries” form the bedrock of American constitutional governance, whose ultimate goal is to safeguard “ordered liberty.” These new challenges demonstrate that Trump is circumventing these “structural worries” and harming “ordered liberty” in the process.

There’s also clear precedent for allowing states to take up this kind of challenge. When President Barack Obama tried to defer deportation for the undocumented parents of American citizens and legal residents, the Supreme Court’s conservatives threw a fit. They accused the president of legislating from the Oval Office and acting without congressional approval. And they succeeded in blocking that program after Texas and 25 other states sued based on an allegation of the flimsiest of hypothetical harms. In that case, Obama was merely executing a statute that allowed him to set “national immigration enforcement policies and priorities,” not building a border wall by fiat in defiance of congressional appropriators. If a president can violate the cardinal principle of separation of powers by stretching congressional guidance, and the states can sue him for it, surely he commits the same constitutional sin against those states by flouting congressional commands.

Litigants have learned well, after two long years of arguing over the travel ban, that the five conservatives have little to no interest in probing what lies in the president’s heart. They simply don’t care about what might or might not be a pretext, or whether tweets should count. They want clinical analysis of formal constitutional authority and presidential power. California v. Trump offers that up on a silver platter: Whatever the president can do—whether his name is Obama or Trump—he cannot take funds Congress refused to appropriate and use them to thwart the will of Congress. No tears, no drama, no probing of the executive’s soul. Just the cornerstone of the Framers’ plan.