We consider the extension of fair event system specifications by concepts of access control (prohibitions, user rights, and obligations). We give proof rules for verifying that an access control policy is correctly implemented in a system, and consider preservation of access control by refinement of event systems. Prohibitions and obligations are expressed as properties of traces and are preserved by standard refinement notions of event systems. Preservation of user rights is not guaranteed by construction; we propose to combine implementation-level user rights and obligations to implement high-level user rights.