High Commissioner for Human Rights Navi Pillay said federations like the United States have a responsibility to ensure that individual states "respect the international responsibilities assumed by the country as a whole."
Humberto Leal Garcia, 38, was put to death Thursday for the rape and murder of a teenage girl in San Antonio. While Leal had lived in the United States since the age of 2, he was still a Mexican citizen and was allegedly not given access to consular representation after his arrest.
The United States is a signatory to the Vienna Convention, which requires foreign nationals to be told of their rights. But the U.S. Supreme Court has ruled the treaty would only be binding on the states if Congress passed a law to that effect.
"I am very disappointed that neither the Texas Board of Pardons and Paroles nor the governor took steps open to them to prevent this breach of the U.S. obligations under international law from occurring," Pillay said.