Jurisdictional sequencing taps into fundamental questions about the nature and role of subject matter jurisdiction and what, if anything, a court may do before it has established jurisdiction. Because the Supreme Court has not rooted the doctrine in a clear theory, jurisdictional sequencing has engendered confusion among judges and scholars, who have been at a loss to explain it. Although a number of courts have embraced the leeway that the doctrine offers—the ability to dismiss a case on easier grounds before taking up harder jurisdictional questions—most scholars have criticized it as illegitimate or incoherent. This Article is the first to offer a theory that both explains the case law and grounds jurisdictional sequencing in a novel vision of subject matter jurisdiction’s precise role. Specifically, I develop a theory of jurisdiction as a surprisingly narrow structural limitation on courts’ power to declare substantive law. According to this view, subject matter jurisdiction protects only institutional values, including separation of powers and federalism, but not personal liberty interests.