In a word, yes.
However, individual cemeteries are allowed to set their own policies.  If a private cemetery wants to require that a family purchase a casket and a vault for the dead body (so it is easier for them to landscape) they are within their rights to do so.
It’s important though, that you don’t let a funeral home or cemetery tell you that buying a casket or vault is the law.  It is not the law.  It is the cemetery’s policy. Any cemetery can choose to offer natural and green burial.