A U.S. Supreme Court majority typically protective of religious liberty voted Thursday night to expedite the execution of a Muslim death-row inmate in the face of what a lower court called a “powerful Establishment Clause claim.”

To University of Virginia law professor Douglas Laycock, it illustrated how religious freedom is often trumped by other issues when they collide at the high court.

For the liberal justices, he said, it’s sex discrimination and sexual-orientation discrimination. For the conservative majority in Thursday’s...