The role of the states in our constitutional system is to protect their citizens and supply tort liability. Where federal law does not preempt state systems of liability, state law supplies the tort- and contract-based rules that govern the vast majority of the relationships in our society and economy. Some think that national rules of liability, or new national choice-of-law rules, should supplant today's state-by-state regulation. But until Congress enacts a comprehensive regulatory scheme, state law will control the causes of action that plaintiffs can bring. And the state law that controls the cause should control the way that the cause is adjudicated - at least insofar as the method of adjudication affects the substance of the right.
Lucas Watkins, How States Can Protect Their Policies in Federal Class Actions, 32 Campbell L. Rev. 285 (2010).