One more puzzle about the twin aims of Erie - the goal in diversity cases of uniformity between federal procedural common law and the law used in a forum state court, to avoid “forum shopping” and the “inequitable administration of the laws" (whatever that means). Since we don't know where the twin aims come from, it's not easy figuring out whether they apply when a federal court is entertaining a state law action outside of diversity. My question for the day is: Do the twin aims apply when a federal court entertains state law actions under the Class Action Fairness Act (CAFA)?
The question isn't whether federal courts sitting under CAFA have a duty to respect state law that the relevant state supreme court wants federal courts to use (although maybe it follows from CAFA that even such state law should be preempted by federal common law). The question is whether the federal procedural common law used by a federal court should borrow from the law that would be used by a forum state court, even if the relevant state supreme court does not care whether its law is used in federal court. Congress can free federal courts of the twin aims if it wants. Has it done so in CAFA?
There is some discussion about whether Klaxon applies when a federal court sits under CAFA. (Klaxon said that a federal court sitting in diversity should use the choice-of-law rules that would be used by a forum state court.) But what about other federal procedural common law issues? Say the question is the method of calculating attorney's fees, exchange rates, or prejudgment interest. Concerning all three federal courts sitting in diversity have borrowed from forum state law. Should they do so when entertaining state law actions under CAFA? If we don't know where the twin aims come from, how can we answer this question?
(Parallel posted on Prawfsblawg.)