In 1971, he authored the Byrd Amendment to the U.S. Federal Strategic and Critical Materials Stock Piling Act. It prohibited the US government from banning the importation of any strategic material from a non-communist country as long as the importation of the same materials from communist countries was also not prohibited. While it did not single out any particular country, it had the effect–intended by its sponsors–of creating an exception in the United States embargo of Rhodesia to enable the import of chromite ore from that country. Rhodesia, run by a mostly white minority government, was unrecognized internationally and under a United Nations-led trade boycott from 1965 following its Unilateral Declaration of Independence from Britain.