In the eyes of Texas Gov. Rick Perry and others, the crisis on our southern border demonstrates the failure of our immigration policy. They are correct, though not in the way they think. The failure in our immigration policy comes from the persistent belief that we can make rivers run uphill.

The sudden flood of underage migrants, sometimes accompanied by their mothers, didn’t happen because border security has been neglected. This administration, like its predecessor, has made a fetish of toughness against anyone trying to get in without authorization. It’s worked, but only up to a point — and often with perverse results. This influx happens to be one of those unanticipated effects.