I've listened to speeches by Thomas E. Wood and his book "Nullification: How to Resist Federal Tyranny in the 21st Century". This is a very popular author of the "Tea Party" and Conservative movements. He makes the same argument as Alan, that it was the Northern states, primarily in the Midwest that were utilizing "nullification" to resist Federal law regarding the capture and return of fugitive slaves and it was the Southern states denying their right to do so, in other words the South was claiming federal law superseded state law and that nullification was illegal. I agree with and accept his conclusions.
Jim