Instructables has a detailed discussion on how to disable an RFID tag in a passport or other radio-enabled item. The bottom line? Smash the bugger with a hammer.
-The last (and most covert) method for destroying a RFID tag is to hit it with a hammer. Just pick up any ordinary hammer and give the chip a few swift hard whacks. This will destroy the chip, and leave no evidence that the tag has been tampered with. This method is suitable for destroying the tags in passports, because there will be no proof that you intentionally destroyed the chip.
Why anyone would want to remove the Mark of the Beast from their passports is beyond me, but if you’re one of those free-love, free-info hippies, feel free to break the law. Just don’t expect us to bail you out of Gitmo.