In 1981, AuCoin won a seat on the House Appropriations Committee, and two years later, was appointed to the subcommittee on Defense appropriations. AuCoin became a legislative critic of weaponizing space, opposing the Strategic Defense Initiative, basing his opposition on probability theory, holding that it could not fully defend the United States in the event of an attack. He also authored a legislative ban on U.S. flight tests of anti-satellite weapons, which carried the force of law unless the president certified that the Soviet Union tested a similar weapon of its own. His amendment effectively legislated arms control for the first time through an act of Congress.