MyServiceHost.Authentication.ServiceAuthenticationManager = new MyAuthenticationManager();

class MyAuthenticationManager: ServiceAuthenticationManager
    {
        public override ReadOnlyCollection<IAuthorizationPolicy> Authenticate(ReadOnlyCollection<IAuthorizationPolicy> authPolicy, Uri listenUri, ref Message message)
        {
            WindowsPrincipal winPrincipal = new WindowsPrincipal(message.Properties.Security.ServiceSecurityContext.WindowsIdentity);

            if (winPrincipal.IsInRole(WindowsBuiltInRole.Administrator))//Собственно сама проверка
            {
                return base.Authenticate(authPolicy, listenUri, ref message);
            }
            else
            {
                return null;
            }
        }
    }

class AuthorizationManager : ServiceAuthorizationManager
    {
        public override bool CheckAccess(OperationContext operationContext, ref Message message)
            {
                //....
            }
    }

class MyAuthorizationManager : ServiceAuthorizationManager
    {
        public override bool CheckAccess(OperationContext operationContext, ref Message message)
            {
                //....
            }
    }