These are the laws designed to protect trade and commerce. The protection is aimed at monopolies, price discrimination, and price-fixing. The Antitrust Division of the Justice Department and the Federal Trade Commission are the agencies that investigate antitrust violations.
In 1890 Congress passed a federal statute, the Sherman Antitrust Act, the prohibits interference with the freely competitive interstate manufacturer and distribution of goods. This statute commonly referred to as the Sherman Act is the governing authority. Congress amended the act by the Clayton Act of 1914.
Another statute, Hart-Scott-Rodino Antitrust Improvement Act, passed in 1976 improves the Justice Department's antitrust enforcement powers. This is the law that requires large companies to give the Federal Trade Commission and the Justice Department notice of intent to merge.