The Privileges and Immunities Clause of Article IV provides: “The Citizens of each State shall be entitled to all Privileges and Immunities of Citizens in the several States.” According to Alexander Hamilton, the clause was “the basis of the union,” which may seem odd given its minor significance in modern constitutional law. Part of the reason for its relative unimportance today is the development of constitutional doctrines unforeseeable in the eighteenth century: the invention of the Dormant Commerce Clause and the enactment of the Fourteenth Amendment, which prohibit much of the interstate discrimination that Article IV’s clause was intended to prevent. However, a major explanation for the unseemly fate of the clause lies with early judges who were not faithful to its original purpose. Courts and scholars have perpetuated their errors.
The clause had one overriding purpose: to assure that Americans were not treated as aliens when in states away from their place of citizenship. It was intended to preserve the benefits that Americans had as British subjects, to be afforded the same as local residents anywhere in the country. The ad-vantages of citizenship (or being a subject) were many, ranging from the protection of life, limb, and property to commercial advantages and access to public resources. The multifarious meanings of “privileges” and “immunities” in eighteenth-century writings show that they encompassed every kind of advantage that came from citizenship. This is why Hamilton could claim the clause was “the basis of the union".
There is compelling reason to conclude that the Privileges and Immunities Clause was intended to guarantee Americans traveling or temporarily residing in another state, or doing business or owning property outside their home states, that they would be treated exactly like the local people, without exception, and regardless of whether the right was recognized by other states, including their own. No court and no scholar has ever reached this conclusion, but it is amply supported by the evidence presented here.