Who was the proponent of the legal theory of Nullification?

John C. Calhoun is recognized as the primary proponent of the legal theory of Nullification, which posits that states have the right to nullify, or invalidate, any federal law that they deem unconstitutional. This theory was a significant aspect of Calhoun's political philosophy, particularly during the early 19th century when tensions between state sovereignty and federal authority became prominent.

Calhoun articulated this theory in response to the Tariff of 1828, which he and others in South Carolina believed unfairly benefited the North at the expense of Southern economies. His arguments emphasized the principle that states could refuse to enforce federal laws that they saw as overstepping constitutional boundaries.

The other figures mentioned also played significant roles in American history but did not champion the theory of Nullification in the same way Calhoun did. For instance, Madison is often associated with the Virginia Resolutions, which advocated for states' rights but did not make a direct claim for Nullification. Thomas Jefferson is linked to similar ideas as well but in a different context, primarily focused on states' rights without explicitly framing them as Nullification. Alexander Hamilton, on the other hand, generally supported a strong federal government and would likely oppose the concept of Nullification.