Slovenia - 1994 Party Law

Part II - Establishment and registration of a party
Title Article 6
Article

6

A Party member may be any citizen who has signed a membership statement, subject to the terms and conditions stipulated herein and/or by any Party by-laws.
In the membership statement the citizen provides their name and surname, birth information, permanent or temporary residence, function, occupation and place of employment and any other information required by the Party by-laws.
A minor who is no less than fifteen years of age may become a member of a youth organization within the Party, and may become a Party member with the written consent of their legal guardian.
The Party must keep a registry of its members.

Categories - Extra-parliamentary party (Membership organization)
Source http://www.uradni-list.si/1/objava.jsp?urlid=199462&stevilka=2110