Gerald S. Dickinson is a constitutional law and property professor at the University of Pittsburgh School of Law.

With the federal government now reopened, President Trump is threatening to invoke the National Emergencies Act as a lever to find money for the construction of a wall on the U.S.-Mexico border — a policy that Congress very clearly does not support. Soon after announcing Friday that he would sign legislation to fund the government for three weeks, Trump declared, “If I don’t get a fair deal from Congress … I will use the powers afforded to me … to address this emergency.” He says he has the “absolute right” to declare a national emergency and order the military to build the wall to stop the threat of “illegal immigration” in the country. But the real threat is the specter of a sitting president wielding emergency powers to implement a public policy he can’t persuade Congress, let alone the public, to support. The law Trump is threatening to use was never meant to allow something like this.

Throughout the mid-1970s, Congress debated whether to terminate certain authorities given to the president to declare a national emergency. In particular, U.S. involvement in Vietnam and Cambodia piqued the interest of several members of Congress, who demanded a special study of the consequences of terminating a 1950 national emergency proclamation regarding the Vietnam War. At the time, the nation had technically been under a state of emergency for more than 40 years. Those emergency powers were extraordinary: The president could, among other things, restrict travel, seize property, organize and control the means of production and assign military forces abroad.

For example, Franklin D. Roosevelt declared a national emergency to combat the Great Depression days after he took office. Harry S. Truman attempted to seize steel mills amid a strike during the Korean War. Richard Nixon invoked the power amid a postal workers' strike. A year later, Nixon declared a national emergency again to impose controls on foreign trade. Although Truman’s exercise of the emergency power was thwarted by the Supreme Court in Youngstown Steel v. Sawyer, the substance of the majority and concurring opinions offer useful insight into today’s debate about circumventing Congress to achieve a policy goal.

Justice Robert Jackson, for example, wrote an extraordinary concurring opinion in Youngstown. He looked to history as a road map for why restraints on executive emergencies powers were crucial to our constitutional republic. Germany’s Weimar constitution, Jackson wrote, was designed to secure civil liberties in the Western tradition, yet “the President of the Republic, without concurrence of the Reichstag, was empowered temporarily to suspend any or all individual rights if public safety and order were seriously disturbed or endangered … in 13 years suspension of rights was invoked on more than 250 occasions. Finally, Hitler persuaded President von Hindenburg to suspend all such rights, and they were never restored. …”

Likewise, Jackson noted that Britain went through both world wars under a “sort of temporary dictatorship created by legislation.” This, some argued, was the “high-water mark in the voluntary surrender of liberty.” But as Winston Churchill noted, the parliamentary regime “stands custodian of these surrendered liberties, and its most sacred duty will be to restore them in their fullness when victory has crowned our exertions and our perseverance.” In other words, Jackson was comforted by “parliamentary controls [that] made emergency powers compatible with freedom . . . only when control [of emergency powers] is lodged elsewhere than in the Executive who exercises them.”

Even the French Republic, which operated under a similar emergency regime called the “state of siege,” was cited as an example of why executive restraints are necessary. Jackson noted that the French had essentially secured limitations in that the emergency powers “could not be assumed at will by the Executive” but, instead, permitted only by parliamentary action.

To temper the potentially dictatorial powers available to the president, Congress stepped in to enact the National Emergencies Act to ensure that proper safeguards were in place to allow for congressional review when the president declared an emergency.

Sens. Frank Church (D-Idaho) and Charles Mathias (R-Md.) were especially interested in getting the act passed as soon as possible. Their bipartisan efforts stand in sharp contrast to today’s hyperpartisan political climate over the border wall fight.

Sen. Lindsey O. Graham (R-S.C.) recently called for Trump to invoke the powers no matter how the shutdown was resolved. Rep. Mark Meadows (R-S.C.) said, “Obviously, a national emergency declaration is an option but it should be the last option used.” Rep. Mo Brooks (R-Ala.) supports declaring an emergency to build an international wall simply because the “United States code says so.”

As co-chairs of the Special Committee on the Termination of National Emergencies, Church and Mathias led a bipartisan effort to study the history of national emergencies. They reported grave concerns about the powers granted to the executive before then. Their objection to granting “absolute” power was founded on legitimate principles of limiting executive powers and, at the very least, giving Congress oversight authority when the president invoked the powers.

It’s clear from the congressional record that Church and Mathias were acutely aware of and sought to prohibit a future president from taking advantage of the emergency powers for partisan and policy purposes. They worked for several years to persuade colleagues to insert provisions into the bill to ensure that Congress would exercise continuing oversight of any future emergencies. Although congressional testimony and legislative history is not binding law, they serve as a useful window to peer into statements made long ago by those who once debated the very law that has generated so much controversy among members from Congress — and the public — today.

Perhaps most enlightening is Church’s testimony during a hearing before the Committee on Government Operations on Feb. 25, 1976. There, he explained that the president “should not be allowed to invoke emergency authorities or in any way utilize the provision of [the National Emergencies Act] for frivolous or partisan matters, nor for that matter in cases where important but not ‘essential’ problems are at stake.

Trump’s threat to declare an emergency is an arguably “frivolous” and “partisan” matter unconnected and unrelated to defending the country from an “essential” problem. Illegal immigration across the southwest border is an “important” problem to address — and Congress has already given, in the Secure Fence Act of 2006, the secretary of Homeland Security the power to take action that is “necessary and appropriate” to secure the border with fencing and patrol. In fact, the offer from Democrats during negotiations to reopen the government to approve additional funding for border security advances prior efforts by Congress under the administrations of George W. Bush and Barack Obama.

But the situation along the border arguably does not rise, in the words of Church, to an “essential” problem now, nor is the construction of a physical contiguous border wall a necessary solution. (It’s hard to take seriously the idea that a years-long construction project is an emergency action, if only because it wouldn’t have any effect until well into the future.) Illegal crossings are at the lowest ebb since the Clinton administration. Although Trump cites migrant caravans as evidence of an emergency, those caravans are not crossing the border illegally but, rather, arriving at legal ports of entry to request asylum, as the law permits. Half of the undocumented immigrants in the United States arrive legally through airports but then overstay their visas. Likewise, there is simply no empirical evidence to suggest that thousands of terrorists are crossing the border illegally.

All this strongly suggests that threatening to invoke an emergency to build the wall is a “frivolous” decision influenced by partisanship, not by responding to an essential problem.

Church’s parting words in his 1976 testimony are noteworthy: “Congress should be forewarned that it is inherent in the nature of modern government that the Executive will seek to enlarge its power in small ways and large.” That’s exactly what Trump is trying to do today.