In which case did the Supreme Court rule that insurance is subject to federal regulation as interstate commerce?

The Supreme Court ruled in U.S. vs. South-Eastern Underwriters Association that insurance transactions are a form of interstate commerce and therefore fall under federal regulation. This landmark decision recognized that the nature of insurance activities, which can involve interstate operations and clients, attributes to their classification as interstate commerce, making them subject to federal oversight.

Prior to this ruling, insurance companies were often regulated at the state level, drawing from the precedent set in Paul vs. Virginia, which stated that states had the authority to regulate insurance. However, the South-Eastern Underwriters case marked a significant shift by emphasizing that the activities inherent in the insurance business cross state lines, thus warranting federal involvement in regulatory matters.

The McCarran-Ferguson Act later confirmed that states would continue to regulate the business of insurance as long as it did not conflict with federal laws; however, it was in U.S. vs. South-Eastern Underwriters Association that the foundational principle for federal regulation of insurance as interstate commerce was established. Insurance Federation vs. New Jersey addresses different aspects of insurance regulation, emphasizing the complexity and multi-layered nature of state versus federal authority, but it did not assert the same foundational change in classification as the South-Eastern Underwriters case.