“FAMILY values do not stop at the Rio Grande,” said George W. Bush. But that may depend on which bank of the river you have in mind. Even by the standards of President Donald Trump’s administration, the way America has begun separating migrant children from their parents is horrific. The policy, part of an effort by the attorney-general Jeff Sessions to curb a seasonal rise in illegal immigration, is repugnant and self-defeating. It is a disgrace to America and should be stopped.

The Obama and Bush administrations both increased deportations of illegal migrants, yet avoided separating migrant families. Mr Trump’s, by contrast, appears to view its right to deprive migrant parents of their children, when pitching them into the criminal-justice system, as a useful deterrent against future immigration. There are reports of migrants having been deported while their children remain in the United States’ foster-care system. Some were not told where their children are or whether they would see them again—and they may not (see article).

Apparently unnerved by the controversy, Mr Trump blamed it on a “horrible law”, which in turn he pinned on the Democrats. It is in fact based on Mr Sessions’s effort to prosecute a lot more illegal entrants. “If you don’t want your child separated, then don’t bring them across the border illegally,” he said. The policy has so far mainly been applied to immigrants charged with a crime, such as crossing illegally more than once. But Mr Sessions also wants to lock up first offenders, who can be detained for up to six months by immigration authorities. In the absence of an increase in family detention centres, that would lead to the break-up of many more families.

It would also put huge pressure on the overburdened foster-care system—which is only one of the ways Mr Sessions’s tough line is likely to be futile. There is little reason to think it will lead to a big drop in illegal immigration. Most migrants are motivated more by their miserable circumstances back home than the prospect of an easy life in America. Moreover, how countries treat migrants is an important advertisement of their character and values, which Americans underrate to their cost. America’s reputation for being fair and decent attracts highly skilled people. It is also among the reasons foreigners trust American diplomacy and admire its culture—despite the erosion of its reputation that has followed Mr Trump’s election.

It’s greater to be good

Mr Sessions’s cruelty will also widen the partisan gulf. It provides more ammunition to those on the left who accuse his party of racism. And that, paradoxically, entrenches Republican support. When accused by Democrats of racism, even moderate Republican voters are liable to defend the policy out of partisan pique. There is little danger of the conscience of the right being awakened by the scandal in the way that European attitudes to migrants from Syria were softened by images of a drowned refugee child.

A wiser government would reassure Americans that today’s levels of illegal immigration are modest by historical standards, far lower than a decade ago. But even if the goal is to cut the number of illegal migrants, there are better ways Mr Sessions might go about it. By recruiting more immigration judges, he could cut the vast backlog of cases that his draconian methods also threaten to make worse. By building more family detention centres he could uphold America’s tradition of decency as well as the law. By handling more asylum cases in Central America, where over half the immigrants originate, he might reduce the flow. Such steps would not only be more humane than terrorising migrants. They might even work.