In carrying out the obligations of the United States under any
migratory bird treaty, the Migratory Bird Treaty Act (40 Stat.
755), as amended [16 U.S.C. 703 et seq.], or the Migratory Bird
Conservation Act (45 Stat. 1222), as amended [16 U.S.C. 715 et
seq.], waters under the control of the Secretary of the Interior
shall be regulated, subject to valid existing rights, to maintain
sump levels in the Tule Lake National Wildlife Refuge at levels
established by regulations issued by the Secretary pursuant to the
contract between the United States and the Tulelake Irrigation
District, dated September 10, 1956, or any amendment thereof. Such
regulations shall accommodate to the maximum extent practicable
waterfowl management needs.