The McCarran-Ferguson Act, passed in 1945, offers a number of benefits to the insurance industry that it would otherwise not possess due to federal antitrust oversight. Among these are:
Exemption from the Sherman, Clayton, and Federal Trade Commission Acts (joint rate-making among property/casualty insurers is one of the activities thus allowed).
Exemption from the "state action doctrine," which allows for anticompetitive conduct as long as that conduct is part of a state policy and is regulated by a state.