Preemption violation? Renfrew Park

I was just on Renfrew park/museum website to register my dog and I noticed that it states.

http://www.renfrewmuseum.org/index.html

"*Special Note about Firearms* They shall not be permitted on the property, except upon authorization of the Board and only for demonstrations of a nature that would conform to the purpose of the park."

Ive been to Renfrew many times armed but I didnt realize I was in violation of their rules because the firearms rule is not posted on any signs.
Heres the thing, I think Renfrew is privately operated but owned by Waynesboro. Their site says the land was willed to Waynesboro but I dont know where to go from there. On their site it says it is operated through an endowment.
Anyone know if Renfrew is private or public?
I dont see it listed as a Waynesboro or Washington township park.