THat's the crux of it. The employer can make it a facet of employment. But, it does appear their posted signs do not hold the force of law (i.e. arrest) behind them. Now, is it actually a stated employment policy? Or did the space rented come with the signs? Sounds like they put up the signs back when CC was allowed, and I'm not sure if they got the owner's permission for it. I wouldn't be surprised if they got permission, or if they didn't, that they easily could. There is no written policy, its just that the signs are up there.