By the 1870s, each state regulated insurance in some manner and most had an insurance department or agency.

Because individual states are responsible for regulating insurance, though they often coordinate their rules, the new rule actually takes the form of 50 individual state laws.

Senate Republican leaders have limited their bill's scope, saying they do not want to usurp states' authority to regulate insurance.

At the same time, though, it exempts from that general rule any state law that "regulates insurance."

Senate Republicans said they had limited the scope of their bill because they did not want to usurp the states' authority to regulate insurance.

The obvious reason for regulating insurance is to guarantee that insurers deliver on their promises.

But the federal law explicitly preserves the states' power to regulate insurance, a field in which the states have set standards for more than 130 years.

The main question before the court today was whether the Kentucky law regulates insurance, as the state contends.

In several recent cases, the court has upheld state laws regulating insurance and managed care.

States have been regulating insurance for more than a century, and the Kassebaum-Kennedy law allowed them to retain a large role.