Enforcing a policy of no ear buds and talking on the phone in the production room

I have an employee that refuses to listen to anyone about violating a policy we have in place. We do not allow headphones to be used on the production room floor for both food safety and product secrecy. Almost every day he has it in his ear and one of the managers has to tell him to remove it and put it in his locker. I have sat down with him twice to explain why it is a food safety risk, his direct manager has had a conversation or two with him about it, and HR has spoken with him about it on a number of occasions. I don't know how or what consequences can be given to him because it would be an even bigger problem if we have to fire him for violation of this policy. 

Any suggestions on what consequences we can use to enforce this policy that does not have to resort to firing him? 

Thanks, at this point any suggestions are helpful!

Our GMP'S spell out the consequences- failure to follow these requires can result in termination of employment.  Hopefully yiu have something like that abd based on that ... fire the employee. 

I agree with the firing of the employee if he continues to violate this policy, however, that in its own way would be causing a whole new issue of having to hire a new person. And because it is so hard to find competent and knowledgeable compounders in my state for 25$ an hour, it seems like it would not be worth it. Any ideas on how to reprimand or consequence the employee w/o having to resort to firing him? 

I would love to think this would be an easy fix, however, I am not very good with confrontation and do not like to reprimand or call people out even though I should be more comfortable in doing so. I have only been SQF and QA/QC Manager for about three and a half months and the employee is even older than me by 13 years. 

Thank you for your response, I do appreciate it

Justine