tc.k you want to allow only admins to create groups only.  And you do not want to allow your users to create any group.  If that is a case you can write a simpple loop that tell the system if the access equals admin, allow creation of groups, and if not do now allow them to create groups.

@fareed - did you yourself read thru http://community.elgg.org/pg/forum/topic/766232/how-can-add-the-ability-only-the-admin-can-create-groups-version-18b2/ ?? it's all in there ;-)

@DhrupDeScoop - Sorry I did not read it and was not aware that the same question was posted 3 times.  Once again my apology.