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.

Trump's executive order denies citizenship to U.S.-born children unless one parent is a citizen or resident, has been challenged in court.

The justices did not address the broader question about whether Trump officials can legally invoke the Alien Enemies Act to target alleged gang members.