[xwiki-users] Global user and local user with Xwiki 6.4 Sub wiki + LDAP account

Hello, Is it possible to force all user in Global user? I (a friend Admin) use LDAP account and 3 subwiki. If new LDAP user log in on a sub wiki (sub wiki URL), unfortunaly a local user is created. Perhaps he must remove "subscribe" right for new user on sub wiki? Thxs for your help (again :) ) Pascal B