After class, Trevor Johnson came up with a scenario in which the Mottleys may have been able to bring their suit in federal district court after all. They could have sued the United States (or officers of the United States) claiming that the federal statute prohibiting free passes was a taking requiring compensation under the 5th Amendment. In that case their cause of action would have been under the 5th Amendment. As such it would have had federal question jurisdiction under 28 USC 1331.
There are quite a few potential problems with this action (for example, is the dispute with the United States ripe enough to count as a case or controversy at all?). But setting them aside, we do indeed have an action that has federal question subject matter jurisdiction.
Of course, this federal action against the federal government is not the same as the state law contract action against the railroad originally brought by the Mottleys. But once the federal action is in federal court, the state law action could be brought in too under...supplemental jurisdiction. We will discuss supplemental jurisdiction later (in excruciating detail). Put briefly, when you have an action (call it A) that has its own source of federal SMJ, actions that would not have federal SMJ if brought on their own can nevertheless be brought in federal court with A, if they concern the same “case or controversy” as A. A classic example of supplemental jurisdiction is when someone sues a state officer in federal court for violation of his federal civil rights due to an arrest and adds to the federal civil rights action a state law battery action against the officer concerning the same arrest. If the officer and the plaintiff are citizens of the same state, the state law battery action will not have its own source of federal SMJ—it could not be entertained by a federal court on its own. But it can be entertained by the federal court with the federal civil rights action.
There are statutory exceptions to supplemental jurisdiction that we will talk about later, but they would not apply to this Mottley scenario. So Trevor has in the end come up with a way the Mottleys’ state law action could have been brought in federal court after all. Bravo.