The FAA rule that prohibits pouring your own is in both 121 and 135 operations
http://www1.faa.gov/avr/afs/cabinsafety/FAR's/121-575.rtf
http://www1.faa.gov/avr/afs/cabinsafety/FAR's/135-121.rtf
The concern stems from according to FAA
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We have received information that indicates drinking of alcoholic beverages by passengers on board air carrier airplanes may be an increasing problem. There have been instances ranging from harassment and/or cruel treatment of flight attendants to physically attacking a male purser.
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The decision by AA to not allow FAs to pour passenger's alcohol is a business decision and not required by FAA.