Final answer:
The Privileges and Immunities Clause of Article IV, Section 2 of the U.S. Constitution prevents states from discriminating against citizens of other states, ensuring civil rights and equal protection, further reinforced by the Fourteenth Amendment.
Step-by-step explanation:
The constitutional provision which prohibits states from discriminating against citizens of other states is known as the Privileges and Immunities Clause of Article IV, Section 2. This clause ensures that citizens shall be entitled to all privileges and immunities of citizens in the several states. For instance, a citizen from one state should receive the same treatment in terms of legal protections, property rights, and access to courts as the residents of another state they are in, ensuring equal protection and civil rights.
Despite this clause, not all treatment must be identical; states may still impose reasonable residency requirements, such as higher tuition for out-of-state students at state universities or voting restrictions to residents only. The Fourteenth Amendment further reinforces protections against state discrimination, providing the Due Process and Equal Protection Clauses that mandate equal treatment under the law and prohibit states from denying anyone within their jurisdiction the equal protection of the laws.