§ 13. Action or proceeding against unincorporated association. An action or special proceeding may be maintained, against the president or treasurer of such an association, to recover any property, or upon any cause of action, for or upon which the plaintiff may maintain such an action or special proceeding, against all the associates, by reason of their interest or ownership, or claim of ownership therein, either jointly or in common, or their liability therefor, either jointly or severally. Any partnership, or other company of persons, which has a president or treasurer, is deemed an association within the meaning of this section.

The service of summons, subpoena or other legal process of any court upon the president, vice president, treasurer, assistant treasurer, secretary, assistant secretary, or business agent, in his capacity as such, shall constitute service upon a labor organization. Such service shall be made on such individuals in the manner provided by law for the service of a summons on a natural person.