Will Baude

And now we're in federal court, which is supposed to apply state substantive law and federal procedural law.

The federal rules of procedure-ish, but state tort law.

And so the question is really, is this kind of rule substance or procedure?

And the standard way this is often conceptualized is what I just said of like, is this procedure or is this substance?

And that's famously impossible to answer because obviously it's both.

It's a procedural rule whose purpose is to make the claim substantively harder to bring.

And you can think of all sorts of rules a little bit like this.

And the court last confronted this general problem in the Shady Grove case you mentioned where it was unable to muster five justices behind one plurality opinion.

I think it was no statutory damages in class actions.

And so class actions are a procedure question, but what are the damages is a substantive question.

And so no substance, none of this kind of substance in this kind of procedure is both substance and procedure.

In a pretty short opinion by Justice Barrett, the court says this law doesn't apply in federal court.

The court says, I think sort of implicitly adopts the plurality opinion, the Scalia opinion in Shady Grove as good law.

And also kind of glosses it in a pretty simple and pro-federal rules of civil procedure way, or basically says, look, if there's a rule of federal civil procedure on point, that's pretty much the end of the inquiry because the Rules of Decision Act authorizes the rules of civil procedure.

And so you can't, even if a valid rule of civil procedure displaces contrary state law, even if the state law would qualify as substantive under Erie's test.

And I take it the court's not, including that possibility.

And I take it you could have a rule of civil procedure.

There could be a thing labeled a rule of civil procedure that's not actually a rule of civil procedure, although since the rules of the procedure have to be approved by the Supreme Court, it's hard to imagine how one would be approved.

Like it would be invalid under the rules enabling it.

Right, not unconstitutional under the rules enabling it.