As a U.S. government shutdown drags on, President Donald Trump has told reporters that he’s considering declaring a national emergency in order to get his desired wall on the U.S.-Mexico border, with or without Congress’ cooperation. It would be a drastic action, but he would hardly be the first American president to take extraordinary steps for what he sees as the interest of the nation.

In fact, not only are national emergencies more common than most Americans probably realize, they can also go on for decades — and whether or not Trump declares an emergency for the wall, the nation is already subject to dozens of emergency declarations that are ongoing today.

From Abraham Lincoln’s decision to suspend habeas corpus in 1861 to Harry Truman’s ordering the Secretary of Commerce to seize control of the steel mills amid a 1952 wartime strike, presidents have occasionally seen fit to step outside the bounds of normal government. By proclaiming a national emergency, the President “may seize property, organize and control the means of production, seize commodities, assign military forces abroad, institute martial law, seize and control all transportation and communication, regulate the operation of private enterprise, restrict travel, and, in a variety of ways, control the lives of United States citizens,” according to a 2007 Congressional Research Service report.

But while scholars agree that the power to declare a national emergency is in fact implied within the executive powers given to the President by the Constitution, there’s at least one big difference between Trump’s situation and that of Lincoln or Truman.