What is the correct test to apply in deciding whether an otherwise applicable state law—here, a state law prohibiting provisions in insurance contracts—can be displaced by an ERISA plan's choice-of-law clause?

QUESTION PRESENTED The Employee Retirement Income Security Act of 1974, or ERISA, expressly saves certain state laws from preemption. For those state laws that are saved, federal courts must often decide which state’s law to apply. The question presented is: What is the correct test to apply in deciding whether an otherwise applicable state law—here, a state law prohibiting provisions in insurance contracts—can be displaced by an ERISA plan’s choice-of-law clause?