Nullifier

n.

1.

One who nullifies or makes void; one who maintains the right to nullify a contract by one of the parties.

Noun	1.	nullifier - an advocate of nullification; someone who believes that a state can resist federal laws
	2.	nullifier - an official who can invalidate or nullify; "my bank check was voided and I wanted to know who the invalidator was" Synonyms: invalidator, voider

advocate, advocator, annul, avoid, exponent, invalidate, nullify, proponent, quash, void