Affiliate Marketing Secrets

I’m a sales manager for independent authorized AT&T dealer for direct sales where I hire my sales reps as a 1099 and they get paid on a commission basis.
I have a rep who recently started with me who quit another office where he did the same thing. The problem is the previous company is stating he signed a contract where he could not worth with any AT&T affiliated companies for 1 year within a 100 mile radius or else they would sue him.
It seems like a complete scare tactic to avoid competition swiping up disgruntled workers. In my understanding the only legal way this could be done is if the company compensates the former worker for the time stating he cannot work for another company and if he does, then he is subjected to being taken to court in violation of the money compensated to him for agreeing to do so.
Does anyone have any knowledge on this? He’s a young smart guy and it seems he’s just being bullied.
Also, if it is wrong is there any legal action that can be taken against the other company?
Thanks in advance!