Article IV addresses discrimination by a state against citizens of other states in fundamental activities, including important common callings and access to courts. A discriminatory rule may survive when the state has a substantial reason for the difference and the discrimination bears a close relation to that reason.

The clause does not require identical treatment in every program. A state may reserve some benefits tied to its own public treasury or political community, while a protectionist license fee imposed on out-of-state workers raises a stronger problem. Corporations are not citizens for this Article IV protection.

Identify the discriminating state, the out-of-state citizen, and the activity burdened. Do not confuse Article IV with the Fourteenth Amendment's differently worded Privileges or Immunities Clause, or with the Dormant Commerce Clause, which can address interstate burdens even when citizenship discrimination is not the central issue.

Video lesson: Federalism: Crash Course Government and Politics #4