That makes it legal, but:<p>It obviously doesn't stop an abusive law enforcement agency from ignoring the law, e.g. the New Jersey State Police were notorious for doing that until they got slapped down enough times.<p>The FOPA <i>provides a defense</i>; legally, as a matter of procedure, all it does it allow you to get a case dismissed.<p>And as noted, it has specifically has not stopped travelers in the cited airports from getting arrested when they were forced to take possession of their luggage en route due to a diversion or whatever.  (In fact, if you were to take gun to a hotel in such a situation the FOPA wouldn't protect you at all, would it?)