As a political matter, it’s understandable that Republicans are angered by the outcome of Trump v. Barbara, which finds that children born in the United States are entitled to birthright citizenship under the 14th Amendment even if they aren’t citizens. The policy cheapens American citizenship.

The legal debate centers on the 14th Amendment’s citizenship clause — “All persons born or naturalized in the United States, and subject to the jurisdiction thereof” — which, for over a century, was understood to exclude children of foreign diplomats and invading armies but not those born to visa holders and illegal immigrants.