Originally Posted by
Sykes
Its not just prohibited by policy alone--it's outright illegal to consume any alcohol that is not "served" by the operator of the flight (14 CFR 135.121(a)). Having said that, I don't imagine that they'd care much.
Fair point about the JS rule, although was not enforced when I brought my own to drink on a shuttle once. Aside from JS policy the CFR doesn't mean you can't bring your own. Having said that I've had drinks on empties on multiple carriers where I have just served myself, in fact I can't ever recall a pilot serving me a drink they've just offered to help myself.