In Ex Parte In the Matter of Duncan N. Hennen, the Supreme Court was asked to decide whether a state court had jurisdiction over a case involving an individual who resided in another state. The petitioner argued that since he lived in Tennessee and not Virginia, where the suit was brought against him, then Virginia did not have jurisdiction over his case. The Supreme Court agreed with this argument and held that states do not have authority to exercise judicial power beyond their own borders unless they are specifically authorized by Congress or by treaty between two nations. This ruling established an important precedent for determining when one state can exercise its powers within another's boundaries and has been cited numerous times throughout American legal history as support for jurisdictional limits on states' courts.

In Ex Parte In the Matter of Duncan N. Hennen, Chief Justice Taney delivered a dissenting opinion in which he argued that Congress did not have the power to pass laws regulating slavery in any state or territory. He reasoned that since slavery was an issue regulated by each individual state, it could not be subject to federal regulation and thus Congress had no authority over it. Furthermore, he stated that if Congress were allowed to regulate this matter then they would also be able to interfere with other matters such as marriage and divorce which are traditionally left up to states' discretion. Therefore, Taney concluded that allowing Congress's law on slavery would lead down a slippery slope of congressional interference into all areas of life previously reserved for states' control and should therefore be struck down as unconstitutional.