That depends on the policy of the employer, doesn't it? If the employer policy is that you cannot have the cell phone on the premises at all then the employee needs to leave that phone outside the business premises. There is nothing illegal about an employer having that kind of policy. You say that you can have anything in your pocket at work and it is only the use of the item that is a problem. Would you say the same thing if the item was a firearm? I know of several employers that ban bringing firearms on the premises, and it is perfectly legal for them to do so. The cell phone is no different.

