Bottom line is: If it's against company policy (and I'm sure it's like that in 99% of the companies out there), don't do it. If you do, AND get caught. You're gone. What's so hard to follow about that? You break the rules, you find another job.
Drinking is legal, smoking pot is not. You can't argue that. If pot WERE legal, you'd be able to buy it at Speedway or the local carry out. You can't.