Congress passed the Neutrality Act of 1939 (the revision of the 1937 act), allowing for arms trade with belligerent nations on a cash-and-carry basis, thus in effect ending the arms embargo.
Furthermore, American citizens and ships were barred from entering war zones designated by the President, and the National Munitions Control Board was charged with issuing licenses for all arms imports and exports. Arms trade without a license became a federal crime, with a penalty of up to two years in prison.