Short answers, pulled from the story.
The Export Control Act of 1940 was a United States law originating as a presidential proclamation by Franklin D. Roosevelt. It was designed to prevent scarcity of critical commodities in a likely prewar environment and to limit the export of materiel to Imperial Japan, with the goal of pressuring Japan to curtail its occupation of the coast of Indochina.
The initial embargo covered airplanes, aircraft parts, machine tools, aviation gasoline, chemicals, and minerals. Iron and steel scrap were added in September 1940. Oil and steel export bans took effect between June and August of 1941, after officials concluded that cutting off oil earlier would be too provocative given Japan's dependence on American oil.
The United States gave six months' notice of withdrawal from the 1911 commercial treaty with Japan in July 1939. Japan's status as a most favoured nation under that treaty legally prevented the United States from imposing retaliatory trade measures, so withdrawing removed the primary legal obstacle to an embargo.
The Mutual Defense Assistance Control Act of 1951 directed the president to enlist the cooperation of other nations in enacting trade controls on the Soviet bloc to parallel those of the United States. Nations that refused to cooperate faced the withholding of benefits from American economic and military aid programs.
The Export Control Act was renewed repeatedly after World War II. The Export Control Act of 1949 was extended in 1951, 1953-1956, and again in 1958, driven by Cold War national security and foreign policy concerns, particularly following the outbreak of the Korean War.
In 1982, Bell Labs's chess-playing computer known as Belle was impounded by US authorities before it could travel to Moscow for an exhibition. The incident illustrated that export controls under the law applied to advanced technology even when it had no direct military purpose, as the computer was classified as a strategic asset.