Whatever one’s worries about the scope of federal courts’ power to create federal common law, everyone agrees that they must have some power to create procedure, that is, common law rules that govern the means by which causes of action (including state law actions) are litigated in federal court. But what happens when a matter is governed by a federal procedural common law rule and by the state law action under which the plaintiff sues? Which wins out?
In Byrd, Justice Brennan said that state law always wins: “It was decided in Erie R. Co. v. Tompkins that the federal courts in diversity cases must respect the definition of state-created rights and obligations by the state courts” – including rules “bound up with these rights and obligations.”
Even if Brennan is right, was this really decided in Erie? And is he right? Assume that service in federal court is not governed by Fed. R. Civ. P. 4, but by a federal common law rule. A plaintiff sues under Pennsylvania law in federal court in New York. Can Pennsylvania really constitutionally compel the federal court to use Pennsylvania's service rule just by binding it up with the Pennsylvania action?(This is parallel posted on Prawfsblawg.)