There are two main ways for a lawsuit to end up in federal court. First, if the lawsuit “arises under” federal law. This is sometimes called federal question jurisdiction. Second, if there is diversity jurisdiction. There are, in turn, two main requirements for diversity jurisdiction: the amount in controversy must exceed $75,000 and all of the plaintiffs and all of the defendants must be citizens of different states at the time the suit is filed.
Probate matters are generally considered matters of state law. To that end, federal court have created a probate exception to federal jurisdiction. “The probate exception is a judicially-created limitation on federal court subject matter jurisdiction, which prohibits the exercise of jurisdiction even where, as here, all the prerequisites for diversity jurisdiction are otherwise present.” Sianis v. Jensen, 294 F.3d 994, 997 (8th Cir. 2002).
According to the US Supreme Court, the probate exception applies to three types of cases: the probate or annulment of a will, the administration of a decedent’s estate, and the exercise of in rem jurisdiction over property already asserted within the in res jurisdiction of a state court. Marshall v. Marshall, 547 U.S. 293, 312 (2006).