nullification

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The act of nullifying or the state of being nullified.
• noun The action by a state not to enforce a federal law as improperly encroaching on the scope of state power.
• noun A theory justifying such action.

from The Century Dictionary.

• noun The act of nullifying; a rendering void and of no effect, or of no legal effect; specifically, in U. S. hist., the action of a State intended to abrogate within its limits the operation of a federal law, under the assumption of absolute State sovereignty.

from the GNU version of the Collaborative International Dictionary of English.

• noun The act of nullifying; a rendering void and of no effect, or of no legal effect.
• noun (U. S. Hist.) the right claimed in behalf of a State to nullify or make void, by its sovereign act or decree, an enactment of the general government which it deems unconstitutional.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The act of nullifying; a rendering void and of no effect, or of no legal effect.
• noun removal

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the states'-rights doctrine that a state can refuse to recognize or to enforce a federal law passed by the United States Congress
• noun the act of nullifying; making null and void; counteracting or overriding the effect or force of something