It is possible to have a 10% service connection disability.
If the National Government wants to pass a law for Federal Parks which are maintained by the federal government that might be ok but to put a state mandate on state parks is a 10th amendment thing. The state may have an over abundance of money and may also want to honor their veterans from their state only. That should be up to the state involved.
I am 100% serviced connected and I always pay full price as a contribution to the state or federal park for their services they provide in the park. The last National park we were in was YellowStone and we paid full price. It was very beautiful and take very good care of. We were on my motorcycle from Louisiana
Alexandra for your information any veteran with a service connected disability even 10% can be seen at the VA for that disability problem. This would be things like hearing loss they can go to the VA and get in the audiology clinic and get retested and get free hearing aids and batteries for free for the rest of their lives.