Or if you want to stray a little bit into sci-fi you could say that HR is the only law either because corporations exist as their own legal countries in some dystopian future or because the corporation owns the planet or space station or whatever this exists on. But have the culture of the corporation very similar to what we all experience in work ala Douglas Adams or Terry Pratchett.
Lets be clear though its HR policy that's gone not common law, so where you could get drunk or even be high in the office depending on the state you could still be arrested for certain behaviors?
Well jeeze I've got so many followers I might as well get the draft going!