Allow me to correct you there. Management can indeed join the union. They just can't have their dues withheld from their paychecks-they have to write a check directly to the union. They can also have union help in preparing their MSPB and FLRA complaints.
It isn't the Red Book that gives management the right to join. It is Title 5. Even with supervisory duties, a manager can still join. Oh, and there are EIGHT different unions within AAFES. Which one are you referring to?