Peltier's attorney, Martin Garbus, says they got a letter from the White House yesterday night saying their application has been denied.
Garbus says Peltier is upset and considers the decision a death sentence.
Peltier's supporters say he was wrongly convicted in the killings of FBI agents Jack Coler and Ronald Williams during a shootout on the Pine Ridge Indian Reservation in 1975. He has exhausted his appeals and his parole requests have been denied. They saw the clemency request as their last chance for winning his freedom.