My Erie question for the day is yet another puzzle about conflicts between state law and federal procedural common law. In Byrd, Justice Brennan said that it followed from Erie that a state rule bound up with a state cause of action must, as a constitutional matter, trump competing federal procedural common law. Yesterday, I asked why a state couldn’t extend its law to a federal courtwithout binding it up with a cause of action. For example, it might want its attorney-client privilege law to extend to any court, federal or sister state, assessing the admissibility of communications made in New York between a member of the New York bar and a client, even if the cause of action entertained by that court is not under New York law. Would New York's attorney-client privilege law trump any competing federal procedural common law on the matter?
Today’s question concerns yet another way that a state might extend its law to federal courts. What if a state wanted its law to extend only to federal courts within its borders? Assume, for example, that the New York Court of Appeals held that New York's attorney-client privilege law extends to federal courts in New York—whether they are entertaining actions under New York, sister state, or foreign law. Would New York law trump federal procedural common law on the matter? Or is a state not even permitted to target the procedure of federal courts in this fashion?
(This is parallel posted on Prawfsblawg.)