For which sector does the McCarran-Ferguson Act grant regulatory powers to states?

The McCarran-Ferguson Act specifically grants regulatory powers to states concerning the insurance sector. Enacted in 1945, this landmark legislation was designed to affirm the states' authority to regulate insurance companies and their operations without interference from federal legislation, unless such laws specifically relate to insurance.

This act acknowledges the principle that insurance is fundamentally a state-regulated industry due to the local nature of the insurance business, which includes things such as underwriting and the claims process. This allows states to establish their own standards and regulations and provide consumer protections that cater to local needs.

Other sectors, like banking, telecommunications, and transportation, are primarily regulated at the federal level or involve a mix of federal and state regulation but are not covered by the provisions of the McCarran-Ferguson Act. Therefore, the association of this act with the insurance sector clearly identifies it as the accurate answer.