The Supreme Court has over the years defined the right to travel (or the freedom of movement) as one of the “unenumerated rights” of the Constitution. Specifically, the Supreme Court has ruled that this right to travel includes the right of citizens to move freely between states, the right to be treated equally in all states when visiting, and the rights of new citizens to be treated like longtime citizens of a state.
The United States Constitution, What It Says, What It Means, A Hip Pocket Guide