My son was evicted from living with us due to the RV Park management. Although the problem was not with them it was with his parents. Since then he has gone to Rehab and has finished his program fro 16 months. He is totally different and will need to move back home as he has no where else to go? We are between a rock and a hard place and need to know if his eviction can be lifted.
He needs to start his life over and I cannot figure out how he can prove himself loyal?

The owner of the park gets to make the rules - and apparently your son has violated the rules to an extent that he had to leave, with or without you. Good that he's been able to get his life back together but the park is under no duty to take him back. If he must live with you then you will have to move.

You can always approach the park and explain the situation but I'm pretty sure management will believe you couldn't control his behavior before and probably can't control it now.

If he has successfully completed a rehab program, and the program is willing to write a letter to the park management, they may relent on a trial basis. Worth a try.

But the park makes the rules and are under no obligation to let him back.

Agreed, it is up to the park management.

I would sure be looking for alternatives for him since the park may not allow him back, such as a halfway house so he can continue his rehab program, and get guidance and support to keep him on track. Talk to the people at his rehab if he hasn't already.