I live in New Jersey, my fiance works a full time job and occasionally works part time job at night. His full time job is sticklers on overtime and rarely give it out. He works for a company that takes care of housing issues on military base. They insisted he take another call and work longer. When he told them he needed to leave he has prior engagements, they argued with him then he finally said he has another job to get to. His boss said he is not allowed to work another job, its a conflict of interest. Can they do that? Dictate whether you have can or can not work a second job in your free personal spear time?

Is there anything that he signed when he hired onto this job that indicated he could not have another part time job?

He said no, that his original boss who hired him that quit a few months ago knew he had another job.

A company can require overtime, so they can give him a warning and a poor job rating if he can not work scheduled overtime.

The issue is, the can not "make him" but they can fire him for not working overtime when asked. So even if he is right, all that happens he gets to collect unemployment.

So it is common when you have to work over on your main job, you have to call in and not go to work on second job.