No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.
Amendment XIV
Section 1.
All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the state wherein they reside.
[1] No state shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States;
[2] nor shall any state deprive any person of life, liberty, or property, without due process of law;
[3] nor deny to any person within its jurisdiction the equal protection of the laws.
[1]
Privileges or immunities
The Privileges and Immunities Clause prevents discrimination against people from out of state, but only with regard to basic rights. The Court uses a two-part test to determine if the Privileges and Immunities Clause has been violated.
First, the Court looks to see if a law discriminates against people from out of state regarding fundamental rights (e.g. protection by the government of the enjoyment of life, and liberty, the right to acquire and possess property of every kind, and to pursue and obtain happiness and safety).
Second the Court focuses on whether the state is justified in the discrimination. It examines if there is a substantial reason for the difference in treatment, and if the discriminatory law has a substantial relationship to that reason. For example, the Court has asked: "Does the distinction made by Montana between residents and nonresidents in establishing access to elk hunting threaten a basic right in a way that offends the Privileges and Immunities Clause?" ... The court held it did not, because hunting is a recreational sport, which is outside the fundamental rights protected by the Constitution. If the court had found that recreation and sports were fundamental rights, it would have still had to examine whether the state had a compelling interest (protecting elk herds from being over-hunted), and whether the law was designed to address that problem.
I'll note that certain activities are quite legal to grant to a state citizen and not to an out-of-state visitor such as the right to vote in state and local elections or to run for public office. Or, to hunt elk as the USSC noted above.
[2]
Due Process
The Due Process Clause prohibits state and local government officials from depriving persons of life, liberty, or property without legislative authorization. This clause has also been used by the federal judiciary to make most of the Bill of Rights applicable to the states, as well as to recognize substantive and procedural requirements that state laws must satisfy. Any location deemed unauthorized by a state legislature has, by definition, been enacted with legislative authorization.
[3]
Equal Protection -
All citizens of the state are protected equally, no one by virtue of race, religion, hair color, former condition of servitude or state of citizenship is affected in any way differently than any other citizen of the state or any other state.
Again, my point is that this addresses no problem that a state may not address itself as was done with the Driver's License Compact.