So I can partake in an alcoholic beverage during my lunch break? Screw my company for telling me otherwise.
A better analogy would be questioning whether you can partake in an alcoholic beverage during your vacation
Not it wouldn't be.
NFL policy states the players are subjected to drug testing and if they fail they face discipline.
My company's policy states that no alcohol consumption during working hours.
The point being that something being legal, doesn't mean that a private corporation/business can not make it against company policy.
If this helps, I deal with a lot of confidential information. If I tweeted some of it out to the twittersphere during my vacation, it would not sit well with my employers. But I am legally allowed to have a twitter account.