Eight justices—the exception being Ketanji Brown Jackson—seem keen to rein in universal injunctions. But a majority also appear committed to averting Mr Trump’s radical departure from the constitution’s promise of citizenship. The justices could thread that needle in three ways.

The Supreme Court could create a patchwork of citizenship rules that echoes a dark time in the nation's history.

The Supreme Court hears arguments in Trump v. CASA, Trump v. Washington, and Trump v. New Jersey, a case about judges stopping President Trump's executive order that limits birthright citizenship for children born to undocumented parents.