Persons of Celtic heritage holding genuine titles of nobility are eligible for Class I membership, which is hereditary. For hereditary membership one must demonstrate proven Celtic lineage, from an ancestor in Scotland, Ireland, Wales, Corwall, Northumbria, Brittany, Man, Celtic Spain, etc.
Those holding ranks in Orders less than that of Knight, as well as members of Colonial Wars and the Cincinnati, are eligible for Class II. Classes II and III are non-hereditary. Each hereditary member of Class I may designate a single heir. The society has been limited to fifty members, but this requirement has been expanded to 150, with fifty per class.