Short answers, pulled from the story.
The Neutrality Act of 1935 imposed a general embargo on trading in arms and war materials with all parties in a war. It declared that American citizens traveling on warring ships traveled at their own risk and set to expire after six months.
Congress passed the Neutrality Act of 1937 on the 1st of May 1937. This new act included earlier provisions without an expiration date and extended them to cover civil wars as well.
The Neutrality Act of 1939 allowed for arms trade with belligerent nations on a cash-and-carry basis, effectively ending the arms embargo. The National Munitions Control Board became charged with issuing licenses for all arms imports and exports, making unlicensed arms trade a federal crime.
Charles Winters, Al Schwimmer, and Herman Greenspun were convicted under this act after smuggling B-17 Flying Fortress bombers from Florida to Israel during the Arab-Israeli War. Winters was sentenced to 18 months in prison and fined $5,000 while Schwimmer and Greenspun were each fined $10,000.
Many provisions of the Neutrality Acts were repealed on the 17th of November 1941 following the sinking of the U.S. destroyer while dropping depth charges on German U-boats on October 31. Merchant vessels were then allowed to be armed and carry any cargoes to belligerent nations.