I am a lawyer in CT and practice in this area of the law.  Employers are permitted to make rules regarding cell phone use at work.  employees have the choice to work for an employer with these rules and the employer may fire any employee for violatring their rules.  i suggest that the employee follow the rules if they want to keep their job.  I would also be mindful of tattle tales at work and use more discretion as to when you use the phone and who is around.  the employer acted within thier discretion.