Enabling discretionary data access control in a cloud computing environment can begin with the obtainment of a data request and response message by an access manager service. The response message can be generated by a data storage service in response to the data request. The access manager service can identify owner-specified access rules and/or access exceptions applicable to the data request. An access response can be determined using the applicable owner-specified access rules and/or access exceptions. Both the response message and the access response can indicate the allowance or denial of access to the requested data artifact. The access response can be compared to the response message. If the access response does not match the response message, the response message can be overridden to express the access response. If the access response matches the response message, the response message can be conveyed to the originating entity of the data request.