Which U.S. law, enacted in 1945, confirmed that insurance regulation generally belongs to the states?

The McCarran–Ferguson Act of 1945 confirmed that insurance regulation generally belongs to the U.S. states.

Before the act, the Supreme Court’s 1944 decision in United States v. South-Eastern Underwriters Association held that insurance transactions could fall under federal regulation of interstate commerce. That ruling raised the possibility of a much larger federal role in insurance oversight.

Congress responded with McCarran–Ferguson, preserving state authority over insurance while allowing federal law to apply when it specifically addresses insurance. The act also limited the reach of some federal antitrust laws, subject to important exceptions.

The statute is not an absolute declaration that states exclusively control every insurance matter. Federal laws such as those concerning terrorism risk, employee benefits, securities, and financial reporting can still affect insurers.