As President Trump considers whether to declare a national state of emergency to build his border wall, few Americans realize they have lived under nearly 30 states of national emergency for most of their lives. Emergencies come and go, but emergency declarations remain. The oldest national emergency still on the books was declared by President Jimmy Carter during the Iran crisis 40 years ago. There are presently national “emergencies” covering everything from vessels in Cuba to democratic processes in Zimbabwe, from exports to cyberwarfare and narcotics trafficking.

National emergencies have long been a tool used by presidents to grow executive power and enable presidential action at the expense of congressional deliberation. In the 1970s, when Congress was concerned about executive power in the wake of Watergate and the Vietnam War, the National Emergencies Act was passed and signed by President Gerald Ford in 1976. However, the law did not limit presidential emergencies as intended. Beginning with President Bill Clinton, who invoked 17 national emergencies, government by national emergency has only grown.

Supreme Court Justice Robert Jackson foresaw the likelihood of national emergencies becoming a favored tool of the executive branch when the court reviewed President Harry Truman’s emergency declaration taking over steel factories. Jackson wrote, in the 1952 Youngstown Sheet & Tube Co. vs. Sawyer, that the “Founders knew what emergencies were, knew the pressures they engender for authoritative action, knew, too, how they afford a ready pretext for usurpation.” Jackson added, “We may also suspect that they suspected that emergency powers would tend to kindle emergencies.”

By now, with nearly 30 national emergencies in effect at all times, we can say that Jackson was right. Presidents find emergencies where they want to act unilaterally, either because Congress is too slow or it is opposed to what the president wants to do. Professor Kim Lane Scheppele rightly concludes that national emergencies are “like a toggle switch, and when the President flips it, he gets new powers.” Legal expert Patrick Thronson points out that “each emergency activates powers in over 160 provisions of statutory law, dozens of presidential orders, and numerous other federal regulations.”

National emergencies, then, have become a weapon in the presidential pursuit of greater power. Alongside their close cousin — declaring war on domestic policy problems such as poverty, crime, terror, energy consumption and drugs — it has skewed the system away from deliberation and toward unilateral executive action. The increase in the use of presidential executive orders is yet one more arsenal in this steady expansion of presidential power at the expense of Congress.

But national emergencies also remind us that executive power has grown not only because of the ambitions of presidents but also because Congress has passively complied. The National Emergencies Act calls upon Congress to vote every six months on whether a national emergency declaration should continue, and this they have failed to do. Congress also has spending and oversight powers it could exercise in national emergencies, but it rarely does.

It would be difficult to argue that something as complex as immigration has suddenly, overnight, become a national emergency requiring unilateral presidential action. It would be more accurate to say that politicians have been arguing for years about what approach to take to complex issues such as Dreamers, the families of immigrants, illegal immigrants performing valuable services, and so on. It is this failure to address a complex set of issues and reach agreement that is the problem, not a sudden change in conditions of the sort that would lead to an emergency declaration.

The national emergency question, then, is not merely about immigration. It is fundamentally about executive power and the role of Congress. If we are prepared to say one more time that Congress is not important and should not be engaged in major immigration policy then, sure, why not have one more national emergency?

David Davenport is a contributor to the Washington Examiner’s Beltway Confidential blog. He is a research fellow at the Hoover Institution.