What federal law allows the federal government to regulate insurance companies only when they are not regulated by state law?

The McCarran-Ferguson Act is a significant piece of legislation that gives states the primary authority to regulate the insurance industry. It was enacted in 1945 and establishes that federal regulation of insurance companies applies only in instances where the states do not have regulations in place. Essentially, this act affirms the historical tradition of state regulation of insurance, emphasizing the importance of state law in governing insurance practices.

This makes the McCarran-Ferguson Act a vital law in understanding the balance between state and federal oversight of the insurance sector. It ensures that states retain control over the insurance market while allowing for federal intervention when necessary, thus promoting a dual regulatory system.

In contrast, the other options do not accurately reflect this foundational principle of insurance regulation. The Insurance Regulatory Act and the Federal Insurance Act do not exist as specifically named legislation that delineates the state-federal relationship over insurance regulation. The National Insurance Policy Act does not pertain to the regulation of insurance companies but rather deals with policy standards. Therefore, the McCarran-Ferguson Act is the correct reference for federal regulation's conditional applicability in relation to state laws governing insurance.