As a result, the president has access to emergency powers contained in 123 statutory provisions, as recently calculated by the Brennan Center for Justice at NYU School of Law, where I work. These laws address a broad range of matters, from military composition to agricultural exports to public contracts. For the most part, the president is free to use any of them; the National Emergencies Act doesn’t require that the powers invoked relate to the nature of the emergency. Even if the crisis at hand is, say, a nationwide crop blight, the president may activate the law that allows the secretary of transportation to requisition any privately owned vessel at sea. Many other laws permit the executive branch to take extraordinary action under specified conditions, such as war and domestic upheaval, regardless of whether a national emergency has been declared.

This legal regime for emergencies—ambiguous constitutional limits combined with a rich well of statutory emergency powers—would seem to provide the ingredients for a dangerous encroachment on American civil liberties. Yet so far, even though presidents have often advanced dubious claims of constitutional authority, egregious abuses on the scale of the Japanese American internment or the post-9/11 torture program have been rare, and most of the statutory powers available during a national emergency have never been used.

But what’s to guarantee that this president, or a future one, will show the reticence of his predecessors? To borrow from Justice Robert Jackson’s dissent in Korematsu v. United States, the 1944 Supreme Court decision that upheld the internment of Japanese Americans, each emergency power “lies about like a loaded weapon, ready for the hand of any authority that can bring forward a plausible claim of an urgent need.”