It depends on whether the Supreme Court will make a decision before 2012 (or later should he be re-elected). If they decide and he is found ineligible, he will not be able to sign anything ever again.
After the Supremes conference on Hollister v Soetoro today, there is no Obama eligibility appeal on their docket for the rest of 2011.
Look up the “de facto officer” doctrine and you’ll see that no actions of Obama’s would be invalidated by a later finding of ineligibility.
(a) The Supreme Court shall have original and exclusive jurisdiction of all controversies between two or more States.Obama can not pass any further law upon immediate decree he is ineligible, should the case ever be decided and the decision claims the Natural Born Citizen clause is what it is supposed to mean.
(b) The Supreme Court shall have original but not exclusive jurisdiction of:
(1) All actions or proceedings to which ambassadors, other public ministers, consuls, or vice consuls of foreign states are parties;
(2) All controversies between the United States and a State;
(3) All actions or proceedings by a State against the citizens of another State or against aliens.