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U.S. Statutes
At the federal level, the principal antitrust acts include the Sherman Antitrust Act, the Clayton Act, and the Federal Trade Commission Act. All three have been codified in Title 15 of the United States Code.
U.S. Regulations
Most regulations are under Title 15: Commerce and Foreign Trade of the C.F.R. (Westlaw link provided here), but note that antitrust regulations are found throughout several titles of the C.F.R., so it is important to research thoroughly.