No idea if it's a real law or just an urban legend, but if you keep it on the down low the FA has better things to do. I've rarely had occasion to BYOB on board, but when I do, I'm discreet. Give the FA a little deniability. Don't ask for a cup of ice -- ask for a cup of ice and a can of club soda or sparkling water. And don't get loaded. One or two drinks to ease the stiffness of travel should be your limit. I've never been told anything. Obviously I'm not a lawyer. If you do this, get arrested, and are executed at high noon by a firing squad, don't blame Peachfront.