The US Department of Justice on Wednesday executed Lezmond Mitchell, a 38-year-old member of the Navajo Nation who had been sentenced to death for the murder of Alyce Slim and her granddaughter, Tiffany Lee, in 2001.

Mitchell’s death marks the fourth federal execution since the revival of federal capital punishment earlier this year. However, Mitchell’s death differs from the other three in that typically tribal members cannot be executed without tribal permission.

Under the Federal Death Penalty Act of 1994, the Navajo Nation chose to opt out of the death penalty. Mitchell and both victims were Navajo members, and the murder occurred on the Navajo Indian reservation in Arizona. However, Mitchell’s conviction, “carjacking resulting in death,” does not qualify for the tribal option. Therefore, the federal government could legally execute Mitchell without the consent of the Navajo Nation.

Despite the nuanced legality of the execution, many tribal leaders have criticized Mitchell’s execution as an “affront” to tribal sovereignty. Jonathan Nez, the president of Navajo Nation, noted that the “federal government ignored the Navajo Nation” by overriding their decision regarding Mitchell’s execution.