I T IS A familiar pattern. The president says something outrageous—this time Donald Trump told four black and brown-skinned Democratic congresswomen, all of whom are US citizens and three of whom were born in America, to “go back” where they came from. His supporters, who have come to accept what many of them previously found unconscionable, stay silent. His opponents, rightly appalled, lament what has happened to their country. At the same time the Trump administration makes a big policy change that attracts far less attention—in this case, an edict that directly affects tens of thousands of people a year and overturns half a century of precedent.

Last year 120,000 people claimed asylum, the majority of them at the south-western border. On July 15th the White House announced that claims will no longer be considered unless applicants can prove that they sought asylum in one of the countries they passed through on their way to America, and were rejected. There will be legal challenges to the new rule, because America is party to the 1951 Refugee Convention and because the change may contravene America’s own Refugee Act of 1980. But in the meantime anyone who passes through Guatemala or Mexico on the way to the southern border without first seeking refuge there may be turned away.

There is no kind way to enforce immigration law, which by its very existence must squash the dreams of some who wish to migrate (see Americas section). Plenty of asylum-seekers at America’s southern border are not fleeing persecution but crime and poverty. However, this is the wrong way to go about things, for reasons of principle and also of pragmatism.