A lot of people look to Thomas Jefferson or James Madison to understand nullification but, there is also George Nicholas. 

Early in the Virginia Ratifying Convention approval of the Constitution was in doubt.  Many delegates were concerned that the federal government would eventually take on additional, unwarranted powers.  Leading historians often say the turning point in the convention was a speech by George Nicholas.  He told the delegates to think of the legal basis of the Constitution like a contract entered into by 13 individuals.  He then asked a rhetorical question.  If one party agrees to the contract but only under two conditions:

  1. That it would never be construed to impose any additional requirements.
  2. Any attempt to do so would be a violation of the contract.

And, if everyone agreed to those two conditions wouldn’t they be legally binding on all parties?  The answer was self-evident.  Yes.  If that’s the agreement, it would be binding on everybody. 

At that point, Nicholas voiced the obvious conclusion.  In like manner these conditions will be binding on congress.

“They can exercise no power that is not expressly granted them.” ~ George Nicholas (Elliot, J., Madison, J., & Elliot, J. (1836). The Debates in the several state conventions, on the adoption of the Federal Constitution, Volume III. Page 626)

This makes up some of the foundational principles of nullification.  If the feds attempt an unconstitutional act, a state doesn’t have to comply.  And, it can even take measures to stop it from being enforced.