The penalties provided by this section shall not apply to any individual who cooperates or testifies with the Government in the prosecution of a Federal or State offense or who is in a Government witness protection program.
Nothing in this section shall be construed to affect the obligation of the United States to any Indian or Indian tribe arising out of any treaty, statute, Executive order, or the trust responsibility of the United States owing to such Indian or Indian tribe. Nothing in this subsection shall exempt any individual Indian from the sanctions provided for in this section, provided that no individual Indian shall be denied any benefit under Federal Indian programs comparable to those described in subsection (d)(1)(B) or (d)(2).
The denial of Federal benefits set forth in this section shall take effect for convictions occurring after September 1, 1989.