Mark Moller of DePaul has published a commentary at the Cato Institute's Cato-at-Liberty blog, based on an SSRN paper discussed by among others Larry Solum, arguing that key elements of the Class Action Fairness Act run afoul of an originalist understanding of the Constitution's Case or Controversy clause. The Constitution gives federal courts jurisdiction over "controversies between citizens of different states", and the multistate class actions that are CAFA's target might seem to fall squarely within that class. However, Moller accepts as persuasive the argument of Public Citizen's Brian Wolfman that until a state court actually certifies a class of plaintiffs in such a case, the lawsuit has not yet risen to the status of a "controversy" for purposes of federal jurisdiction. Even on this theory, CAFA could be rewritten to accomplish some of its goals in a more cumbersome and less reliable way -- letting the state court decide whether to certify the hoped-for class action, for example, and then taking away jurisdiction once it had done so and a controversy was undeniably at hand.
It should be noted that this interesting theory does not amount to saying that states have some sort of constitutional right to go on resolving multi-state class actions, or that CAFA somehow defies federalism, proves the hypocrisy of its conservative supporters, etc., etc. (although we fully expect to hear some critics say all those things). State-court handling of 50-state class actions poses the more pressing threat to federalist values, because it empowers the plaintiff-selected state to impose its own favored litigation outcomes without so much as asking leave of the states where the transactions took place. (It does not serve a proper understanding of federalism to invite an Illinois state court to second-guess dealings between a Delaware lender with a Nebraska borrower, and preside over a verdict more punitive than either a Delaware or a Nebraska court would have reached. But if forum-shopping plaintiffs can head for Illinois courts, that is what will happen.) Hinging as it does on interpretation of the Case or Controversy Clause, Moller's argument is best suited for evaluation by those steeped in the history and workings of that interesting (and, for most non-lawyers, fairly recondite) Constitutional provision.