Having been rebuffed by Congress in his effort to secure $5.7 billion to build 234 miles of wall along the US/Mexico border, President Trump Friday invoked criminal immigrants and illicit drugs, which he said flow over the border, to declare a national emergency, allowing him to divert billions earmarked for military construction projects, ‘counter-narcotics programs’, and other funds to build his wall. The deal to keep the government open Trump signed almost simultaneously with the declaration of emergency included only one-fourth of the barrier funding he’d demanded to fulfill his signature campaign promise.

Presidents have long declared emergencies (the Civil War and Great Depression among them). Since 1976, when Congress sought to regulate such declarations by passing the National Emergencies Act, presidents have designated more than 58 emergencies, most of them in response to foreign crises, such as when President George W. Bush signed an executive order after the 9/11 attacks empowering the president to reroute military construction money.

Critics have challenged Trump’s declaration on policy grounds, saying the bulk of illegal drugs come through legal ports of entry, and that illegal immigrants commit less crime than native-born Americans. But they also make a legal argument: that Trump is doing an end run around Congress’ stated opposition to funding such a wall, violating the Constitution’s language giving legislators control over appropriations.The American Civil Liberties Union and the state of California are among those saying they’ll challenge the president’s emergency declaration in court. And Democratic congressional leaders have vowed to introduce legislation to block the president’s plan.

The whole point of emergency powers is to enable the government to respond to a sudden crisis that cannot be addressed fast enough by ordinary political processes, not to give the president a blank check to use that authority whenever it might be politically convenient. One of the most basic rules of legal interpretation is that words used in laws must be understood in terms of their “ordinary meaning.” The ordinary meaning of “emergency” is a sudden crisis of some sort, not just any issue of any kind.

If a “national emergency” can only be declared in the event of a sudden crisis, Trump’s declaration clearly doesn’t qualify. Quite simply, there is no crisis at the border. To the contrary, crime and terrorism risks in the border area are very low, and the number of illegal border crossings has been dropping. The vast majority of undocumented immigration is a result of visa overstays, not illegal border crossings at all. Trump also cites the flow of illegal drugs as a justification for the declaration. But 80 to 90 percent such drugs are brought in through legal ports of entry that would not be affected by his proposed wall.

To sum this whole situation up, I’ll end with a quote from reason.com’s Illy Somin, “If Trump’s desire to build a wall qualifies as an emergency, then pretty much anything does. The president would have unlimited power to declare any real or imagined problem an emergency, and thereby tap a wide range of emergency powers.”