If you are doing a normal Clarion Desktop program, then Active Directory support (via LDAP) is included in NetTalk 10 Desktop.
This allows a Clarion Legacy or ABC program to check user access rights against an Active Directory Directory Services server.
NetTalk 10 is scheduled for release in July, 2017, but if you have an urgent need for this, and wish to beta test this class, please let me know.
Cheers
Bruce