When employees are off-premises and unpaid, what can we decree?

Q: Two employees got into a fight while on their lunch break. They were playing soccer in an open lot off premises and wearing their company uniforms. No one was hurt, but the Vice President reacted to the incident by banning all employees from playing any sports during their lunch break while on premises or off. Our employees are not paid for their lunch break and they are not part of a union. Can he dictate what the employees can or cannot do on their unpaid time? – Betts, Illinois