To raise revenue and perhaps also to discourage people from leaving its borders, Nevada, back in the 1860s, imposed a tax of one dollar on stagecoach and railway tickets for out-of-state destinations. In Crandall v. Nevada (1867), the Supreme Court held that the tax was unconstitutional. In ruling as it did, the Court did not point to the language of any particular constitutional provision. None refers expressly to a right to travel from one state to another, much less to a right to travel without being taxed. Instead, the Court found the right to travel among the states, and a prohibition against state legislation penalizing the exercise of that right, to be implicit in the general structure of the Constitution and in the concepts of nationhood and national citizenship.

From a modern perspective, Crandall v. Nevada illustrates two important features of American constitutional law. First, just as existence of the states imposes implied limits on Congress's regulatory powers – a matter discussed in Chapter Seven – so the existence of the federal government and the idea of unitary nationhood impliedly restrict the power of the states.