I think training the gate staff to decide who is..and who isn't drunk would be a hard job. Ive been in the pub game for 24 yrs and i can tell u from personal experience that if u pull an individual out of a queue thats part of a group and tell them that they're holiday is over..before its begun....trust me..there's going to be trouble. Trust me..no one wants that job. You'd have to have a couple or gorillas at each gate..and even then i suspect there would be quite alot of violence...which is why the gate staff let them through in the first place..its non confrontational.