privileges and immunities clause

The primary purpose of this clause, like the clauses between which it is located—those relating to full faith and credit and to interstate extradition of fugitives from justice—was to help fuse into one Nation a collection of independent, sovereign States. It was designed to insure to a citizen of State A who ventures into State B the same privileges which the citizens of State B enjoy. In line with this underlying purpose, it was long ago decided that one of the privileges which the clause guarantees to citizens of State A is that of doing business in State B on terms of substantial equality with the citizens of that State.