An executive order may be nullified:
1. By SCOTUS.
2. By a 2/3 vote of congress.
3. By another executive order. Presidents may supercede or nullify executive orders of their predecessors. Case in point: See Obama executive order 13491 revoking Bush II executive order 13440.
Last edited by thallub; November 15, 2012 at 09:56 AM.