WASHINGTON, May 1 -- The Supreme Court on Wednesday confronted a constitutional question that has defined American identity for more than a century: whether a president can unilaterally restrict birthright citizenship, a principle long understood to be guaranteed by the 14th Amendment.

During more than two hours of oral arguments, the justices, across ideological lines, expressed sustained skepticism toward a directive issued by US President Donald Trump that seeks to deny automatic citizenship to some children born on US soil.

The case, one of the most consequential of the court's term, places at its center a legal and philosophical dispute over the meaning of a single constitutional phrase: "subject to the jurisdiction thereof."

A Co...