A version of this piece first appeared on the blog Impeachable Offenses.

The looming question in the ongoing government shutdown is whether President Donald Trump will, as he repeatedly threatens, declare a “national emergency” to get funding for his border wall if Congress will not pass budgetary authorization for the edifice. Multiple excellent analyses of a president’s legal authority to declare such emergencies have appeared. The upshot of all of them is that the administration could make superficially plausible arguments for such authority but that all such arguments would trigger compelling legal challenges. Moreover, a use of “emergency” powers to circumvent congressional unwillingness to fund a long-wished-for presidential pet project would be both unprecedented and a serious challenge to constitutional separation of powers norms.

What has not been fully addressed is the claim, floated by several commentators, that declaration of a national emergency under these circumstances would constitute an impeachable offense. As a constitutional matter, I believe such a declaration could constitute part of a larger pattern of impeachable conduct. However, three factors would make the political path to impeachment on that ground very tricky. The first is the promiscuity with which Congress has ceded emergency authority to the president. The second is the Supreme Court’s overzealous limitations on the so-called congressional veto—a mechanism for constraining presidential misuse of Congress’ grants of discretion. The third is the distressing likelihood that Republican legislators, blinded by tribalism and cowed by Trump’s enduring popularity with the Republican base, would not defend their own constitutional authority. Let’s walk through the problem.

First, as all but a few outliers concede, impeachable offenses need not be crimes. As George Mason, who introduced the phrase “high Crimes and Misdemeanors” into the constitutional text, observed, the primary objective of the impeachment mechanism is to forestall “[a]ttempts to subvert the Constitution.” Multiple British parliaments, from whose precedents Mason drew the phrase “high Crimes and Misdemeanors,” employed impeachment, not for punishment of statutory crime, but to remove executive officials who “subvert[ed] the ancient and well-established form of government” of Great Britain.

One of the most fundamental precepts of American constitutional government is that Congress makes the laws and, in particular, maintains the power of the purse. Article I, Section 9 of the Constitution is unequivocal: “No Money shall be drawn from the Treasury, but in Consequence of Appropriations made by Law.” The wall dispute is nothing more than an appropriations fight. The president wants Congress to appropriate money for a special purpose—building a border wall—and Congress declines to do so. A president who claims the power to spend $5.7 billion dollars on a project Congress has expressly refused to authorize is therefore in undoubted violation of the most basic separation of powers principle … unless he can claim that Congress has somehow already authorized him to act.

Trump would have a fig leaf of legal justification, and resolving the matter would take months or years.

That’s where the threatened declaration of national emergency comes in. One potentially salutary effect of Trump’s threat is that it has awakened the public to the striking variety of laws permitting a president to claim emergency powers. On the one hand, the existence of such laws is unsurprising. In the modern interconnected world, real threats to the public welfare—war, terrorism, disease, or natural disaster—can arise quickly. Sometimes the federal government is the only entity with the resources for adequate response, and sometimes action will be required before Congress can authorize it. On the other hand, Congress’ choice to delegate emergency power rests on the assumption, the norm if you will, that presidents will not misuse that power to circumvent ordinary constitutional arrangements. Trump is casting a bright and disconcerting light on that happy assumption.

The most likely legal sources of emergency authority for wall building lie in statutes relating to military matters such as 10 U.S.C. Section 2808(a). That act provides that, upon presidential declaration of “a national emergency … that requires use of the armed forces,” the government may “undertake military construction projects … that are necessary to support such use of the armed forces.”

Of course, whatever one’s view of the current situation at the border, there is no serious case that it “requires the use of the armed forces.” Regulating commerce, immigration, and crime at the border are all traditional civilian functions, and there has been no recent change, no “crisis,” remotely justifying military intervention. Moreover, even if one believed that the Army had a useful role to play in border security, it cannot be plausibly argued that building several hundred miles of wall would be “necessary to support” military operations. Indeed, Trump’s approach to the issue would turn the statute on its head. He has not claimed that there are required military operations for which a wall would be necessary support. Rather, he claims that the wall is necessary, and thus, in the absence of congressional authorization to build it, military funds should be diverted for its construction.

But assume that whether under Section 2808(a) or some other statute Trump claims emergency power to build his wall. Opponents would have two possible avenues of response.

First, subject to rules about standing, a variety of folks might sue (Congress itself, individual members of Congress, border landowners, conservation groups, etc.). Three lines of argument seem likely: (a) there is no “emergency” justifying a presidential declaration in the first place; (b) emergency or not, building a border wall doesn’t fit within the parameters of whatever emergency statute Trump chose to rely on (e.g., building a wall is not necessary to support military operations); or (c) the broader contention that this particular declaration of emergency powers is a transparent nullification of the Constitution’s allocation of powers among the branches of the federal government.

Traditionally, courts try very hard to avoid second-guessing presidential decisions in areas where either the Constitution or statutes grant him wide discretionary authority. That said, using emergency powers to authorize a long-debated civilian construction project in the face of congressional refusal to appropriate seems such a flagrant abuse that I suspect the courts would ultimately rule against Trump. Nonetheless, he would have a fig leaf of legal justification, and resolving the matter would take months or years.

Alternatively, Trump’s congressional opponents could invoke the provisions of the National Emergencies Act. That law, passed in 1976, created a mechanism for congressional termination of presidentially declared emergencies. As originally written, such emergencies ended once the president said so or Congress passed a “concurrent resolution” (a resolution by both the House and Senate). In its original form, the law did not involve the president in the congressional termination process; once the concurrent resolution passed both houses, the emergency would be over, regardless of what the president had to say about it.

However, in a 1983 case called INS v. Chadha, the U.S. Supreme Court seemingly voided all so-called legislative vetoes. Chadha involved a statute that allowed a vote by one house of Congress to reverse certain executive branch decisions about immigration cases. The court decided that this procedure violated the constitutional requirement that lawmaking be bicameral, i.e., involve votes by both the House and Senate, and the so-called presentment clauses that require presidential signature before a bill can become law. The primary focus of Chadha was the unicameral nature of the immigration procedure at issue, but Chadha at the least casts grave doubt on the validity of even bicameral congressional veto procedures.

Therefore, in 1985, Congress amended the National Emergencies Act to specify that presidential emergencies terminate when “there is enacted into law a joint resolution terminating the emergency.” This language implies that, to become “law,” the joint resolution would have to be presented to the president for signature. Thus, the president could veto the resolution, leaving the emergency in place unless Congress could summon two-thirds majorities in both houses for an override.

In any previous era of American history, securing a majority or even a supermajority of both the House and Senate to void a president’s blatant nullification of the constitutional appropriations authority of Congress would, I think, have been a cinch. Any rational legislator, even one of the same party as the president, would recognize that acquiescence would badly dilute his or her own institutional power. Not to speak of creating a precedent that would be employed by succeeding presidents of the opposite party.

However, the standards and institutional self-respect of this Congress (particularly, if I may say, its Republican members) are so degraded that it seems entirely possible that all but a handful of Republicans would vote to uphold the emergency declaration—the Constitution and separation of powers be damned.

Which brings us to impeachment. I have no doubt that the founders would have considered presidential abuse of emergency powers to nullify congressional appropriations authority to be impeachable conduct. Invocation of emergency authority in the wall dispute would be unprecedented. It would amount to presidential rule by decree and subversion of a bedrock of American constitutional design.

That said, I suspect even the most doctrinaire constitutionalists might hesitate to impeach a president for a single instance of such abuse. One can fairly argue that Harry Truman’s effort to seize the steel industry for national security reasons in the face of a nationwide strike was a more egregious overstep, and the remedy there was not impeachment but a judicial smackdown by the Supreme Court in the Steel Seizure Case. However, an unwarranted emergency declaration by Trump would not be an isolated misstep but merely a single item in the bill of particulars supporting impeachment for a pattern of conduct destructive of the constitutional order.

The likelihood of a Trump wall emergency becoming part of articles of impeachment would be enhanced if one or both of two things occurred.

First, before Congress could seriously contemplate impeaching Trump for abusing his emergency powers, it would have to have exerted its own authority by voting to terminate Trump’s emergency declaration under the National Emergencies Act. If Congress made no effort to use this tool or failed to secure majority votes in both houses, it would be poorly placed to argue that Trump had committed a major constitutional sin against congressional prerogatives. Congressional termination of the emergency by majority votes including significant numbers of Republicans in both houses would be an especially persuasive indicator that this was a constitutional, and not a partisan, disagreement. Still better (though implausible) would be termination votes by veto-proof two-thirds majorities. Sadly, the events of the past two years give one little confidence that many Republican legislators retain sufficient awareness of constitutional principles or indeed sufficient institutional self-respect to resist their raging leader.

Second, if the Supreme Court definitively rejected Trump’s move as an unconstitutional breach of the separation of powers, the case for impeachment would be significantly strengthened. A ruling against Trump on the ground that he violated the terms of a particular emergency powers statute would also be helpful, though not as compelling. Mere misapplication of statutory language—even if the misapplication is willful and flagrant—has less resonance as a ground for removal than a constitutional infraction. In either case, Trump would surely bluster and denigrate the judges, but a well-reasoned judicial repudiation of Trump’s overreach could stiffen the spines and harden the resolves of Republican legislators now too timorous to do what most know is right.