The three-page letter sent Sunday by James Sullivan, Abbott’s general counsel, said only the governor has the constitutional authority to delay an execution. Sullivan warned that unless the court rejects the subpoena, “it can be repeated in every capital case, effectively rewriting the Constitution to reassign a power given only to the Governor.”

The governor has publicly remained silent as pressure mounted from both sides of the aisle for him to step in on behalf of the death row inmate.