McCarran-Ferguson Act

Federal legislation (Public Law 15) enacted in 1945 providing that even though the insuring or provision of health care may be national in scope, the regulation of insurance is left to the states. Under the Act, insurance is exempt from some federal antitrust statutes to the extent that it is regulated by the states. The exemption primarily applies to gathering data in concert for the purpose of ratemaking. Otherwise, antitrust laws prohibit insurers from boycotting, acting coercively, restraining trade, or violating the Sherman or Clayton Acts.
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Passed by Congress in 1945, this act states that regulation and taxation of insurance by the states is in the public interest and that congressional silence should not be construed as a barrier to state regulation.