subversion need to specify group members in the 'groups' section of svnaccess.conf configuration file. external access control system like LDAP, AD, &etc. requires to syncronize group members to svnaccess.conf (for example: http://thoughtspark.org/node/26/). subversion must query operating system for group members directly. for example: on posix systems from nss (ldap, nis, /etc/group ...). on windows: from AD or local groups.
Original issue reported by dab1818