In Oklahoma, state statutes require ingress and egress to ANY graveyard (public or private) containing ten or more burials. I was told that if a land owner refuses access, to cite the statute to him, then go to the sheriff and tell them the problem and the statute and state that you would like protection when entering under your rights under the constitution and statutes of the state of OK. Luckily, I never had to resort to this.
It may be similar in other states. It was explained that it is "similar" to an easement: REQUIRED access, whether private or not.
Hope this helps. I'm nt a lawyer, but this is how it was explained to me.
Mahlon Erickson