Slovenia - 1994 Party Law

Part II - Establishment and registration of a party
Title Article 4
Article

4

A Party may be established by at least 200 citizens of the Republic of Slovenia of legal age signing the Party Founding Declaration (hereinafter referred to as: "Founding Declaration").
No person whose legal capacity has been revoked may act as a Party founder.

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