In 2015 at the Norman Music Festival, a similar issue took place. A judge ruled that the city could not enforce a no weapons policy on public property even if a private entity leases it. The ruling was later upheld that year. So the entity has the right to say "no guns" but the city cannot tell police officers to enforce the policy for that event.
https://www.news9.com/story/2888178...st-no-guns-policy-at-norman-music-fest-stands
They can't just remove you for having a firearm, but if the management asks you not to enter and/or leave and you fail to do so, then they can arrest you for trespassing. Same as if you walked into a store and the store asks you to leave because you are carrying.