According to Apple Insider, US Federal District Judge Kenneth Karas has issued an order preventing Mark Papermaster from taking his new position as a vice president at Apple, pending a decision over IBM's "no compete clause" inspired lawsuit.
Apple and Papermaster have responded, but Daring Fireball doesn't think they have much to worry about, give "Application Group, Inc. v. Hunter Group, Inc., 61 Cal.App.4th 881 (1998), a California non-compete clause case":