A wise person once said that perusal of the day’s news requires an answer to the question “Is this crisis worth worrying about?” When it comes to the prospect of President Donald Trump invoking emergency powers to build a wall at the border with Mexico, the answer to that question is an emphatic yes.

The political logic for Trump to declare a national emergency in order to build a wall has become increasingly clear. He believes that the wall is an unbreakable commitment to his supporters, but negotiations with Congress over money to pay for it are at an impasse. It looks like an emergency is his only chance to get the wall—and securing funding for it in this way, outside the normal appropriations process, would allow him to start the process of building it, while also signing a bill that would reopen the full federal government. On Thursday, the President seemed to be leaning this way. “If this doesn’t work out,” he said, referring to budget negotiations with Congress, “probably I will do it—I would almost say definitely. This is a national emergency.” In some ways, the emergency option might suit Trump’s Democratic opponents in Congress, too. It would allow the government to reopen before the public starts blaming them, in addition to the President, for the shutdown.

It all makes so much sense—and it would be a sign that the country is rushing toward an authoritarian future. The situation is even more perilous because, in my view, the current law favors Trump. The National Emergencies Act of 1976 is a sloppily written statute that, even though it was passed in response to Watergate, presupposes a level of good faith on the part of the President. This is because the law doesn’t provide a definition of “emergency,” thus leaving that determination essentially up to the Commander-in-Chief. It’s been invoked by Presidents more than forty times, and there are currently thirty-one “emergencies” in effect. Three have been declared by Trump, including one about sanctions on Russia for interference in the 2016 election.

Virtually all of these declared emergencies are uncontroversial; many involve the imposition of sanctions on people involved in human-rights violations in Africa and Central America. Most important, none of them was declared in explicit defiance of Congress’s power to appropriate funds. Clearly, the law was not intended to be used as an end run around Congress, but, given its imprecise wording, the courts may well allow Trump to use it that way. (Indeed, the courts might not even address the constitutionality of the President’s emergency action, because it’s possible that no one, especially not members of Congress, would have standing—that is, the legal right to challenge Trump’s invocation of an emergency. If Trump were to use the emergency powers to seize private land under the doctrine of eminent domain, the owners of that land would have the right to go to court, but the process of identifying the landowners and seizing their land would likely take many months, if not years, meaning that there would be no resolution in the courts for a very long time.)

During nearly two hundred and fifty years of American constitutional history, two things have been true: the power of the Presidency has grown, and Congress has always retained the power of the purse—the heart of its authority under Article I of the Constitution. During that same history, many of the disputes between the executive and legislative branches have been about how much the federal government should spend, and on what. These disputes have ended in one of two ways: with the President signing a budget passed by Congress, or with Congress overriding the President’s veto. If the President can spend government funds without congressional approval—indeed, if he can do so in the face of an explicit congressional refusal to spend funds for precisely the purpose that he seeks—that fundamentally reorders the relations between the branches. Specifically, it vastly expands the President’s power at the expense of Congress.

Even conservatives purport to recognize the risk of this kind of restructuring of the constitutional balance. After all, Trump will not always be the President. On Wednesday, Senator Marco Rubio, the Florida Republican, warned against the practice of emergency spending by the President. “If today the national emergency is border security, tomorrow the national emergency might be climate change,” he said. (He was right about the process if wrong on the issues; climate change really is an emergency.) Still, if the first two years of Trump’s Presidency are a guide, Republicans like Rubio will express their concern and then fall in line behind the President. A Supreme Court anchored by two Trump appointees with a capacious understanding of executive power will likely be no check, either. And, if today’s “emergency” is the need for a border wall, tomorrow’s, as Rubio said, will be a need for something else. Congress, and the American people, will have to live with whatever that turns out to be.