The U.S. southern border has seen a sharp drop in migrant encounters entering between ports of entry at the southern border, according to a CBP source.

This is where Mr Trump’s talk of an “invasion” becomes more than rhetorical bombast. Framing the cartels as terrorists invading America is meant to legitimise his use of the law. And because America is being invaded, Mr Trump argues, he can block anyone from crossing the border. The courts may not see it that way. ■