Mr. Bush, who presided over 152 executions as governor of Texas, wants to halt the execution of Jose Ernesto Medellin in what has become a confusing test of presidential power that the Supreme Court, which hears the case this week, ultimately will sort out.
The president wants to enforce a decision by the International Court of Justice that found the convictions of Medellin and 50 other Mexican-born prisoners violated their rights to legal help as outlined in the 1963 Vienna Convention.
That is the same court President Bush has since said he plans to ignore if it makes similar decisions affecting state criminal laws.
"The president does not agree with the ICJ's interpretation of the Vienna Convention," the administration said in arguments filed with the court. This time, though, the U.S. agreed to abide by the international court's decision because ignoring it would harm American interests abroad, the government said.
Texas argues that neither the international court nor Mr. Bush has any say in Medellin's case.
Medellin was born in Mexico but spent much of his childhood in the United States. He was 18 in June 1993, when he and other members of the Black and Whites gang in Houston encountered two teenage girls on a railroad trestle.
The girls were gang-raped and strangled. Their bodies were found four days later.
Medellin was arrested a few days later. He was told he had a right to remain silent and have a lawyer present, but the police did not tell him that he could request assistance from the Mexican consulate.
Medellin gave a written confession. He was convicted of murder in the course of a sexual assault, a capital offense in Texas. A judge sentenced him to death in October 1994.
Medellin did not raise the lack of assistance from Mexican diplomats during his trial or sentencing. When he did claim his rights had been violated, Texas and federal courts turned him down because he had not objected at his trial. Mexico later sued the United States in the International Court of Justice in The Hague on behalf of Medellin and 50 other Mexicans on death row in the U.S.