"substantial and material contributions to the national defense and security". In addition to its own nuclear weapons, Britain had hosted American Strategic Air Command nuclear bombers since 1948. Congress amended the Atomic Energy Act of 1954 in June 1958, and America and Britain again began sharing nuclear research under the 1958 US–UK Mutual Defence Agreement. The stipulations contained in the Act caused significant controversy during debates over NATO's military command structure. Both Striking Fleet Atlantic and the United States Sixth Fleet have never been allowed to be placed anywhere but directly under American commanding officers—the Supreme Allied Commander Atlantic and Commander-in-Chief, Allied Forces Southern Europe—because the dominant legal interpretation of the McMahon Act has been that nuclear striking forces cannot be controlled by non-US commanders. This was the reason for the formation of Striking Fleet Atlantic as an independent entity, instead of being operationally subordinated to the UK Admiral serving as Commander-in-Chief, Eastern Atlantic, in October–November 1952. This was also the reason why the Sixth Fleet, in its NATO guise as Naval Striking and Support Force, South, was placed under American control rather than Allied Forces Mediterranean when the European commands were agreed at the same time. Case law A 2012 court decision concerning a state law attempting to shut down the Vermont Yankee Nuclear Power Plant affirmed that the Act gives the federal government exclusive authority over safety at nuclear power plants. This allowed Vermont Yankee to continue operating until it was voluntarily shut down by the owner for economic reasons in 2014. Notes References External links Text of the passed McMahon Act (PDF, scanned from the Congressional Record) Text of the submitted McMahon Bill (pp. 77–90) 1946 in American law Arms control Military disbanding and disarmament Nuclear history of the United States Nuclear weapons infrastructure of the United States United States federal energy legislation United States Atomic Energy Commission 79th United States Congress 1946 in the environment History of the Manhattan Project