Privileges and Immunities Clause of Article IV (the Comity Clause)

Privileges and Immunities Clause of Article IV

          Article IV generally is designed to ensure that the United States is one Nation and that state sovereignty should not be so extreme as to destroy national identity. 

          Article IV, §2 provides:

“The Citizens of each State shall be entitled to all Privileges and Immunities of Citizens in the several States.”

The purpose of this provision is to protect the citizens of State A from being treated like non-citizens, like foreign nationals, when they visit State B.  It's like a special kind of equal protection clause protecting citizens of one state when they visit another state. 

State B must treat citizens of State A as welcome visitors to a sister state. The Court has said that when State B discriminates against citizens of another state the issue is whether the interest is "sufficiently fundamental to the promotion of interstate harmony." 465 U.S. at 218.