It sounds simple, doesn’t it? In federal court cases where jurisdiction is based on diversity of citizenship, the court applies the substantive law that a court of the state in which the federal court sits would apply. That’s the Erie doctrine that all law school students learn to love. What’s the problem?

Well, what if the case presents choice of law questions? Would a case involving a defectively manufactured product be governed by the law of the state in which the product was manufactured or the state in which it caused the plaintiff to suffer injury? What if the case would be time barred under the law of the state where the injury occurred, but not under the law of the forum state, where the manufacturer is found?