Rules on Civil Procedure
Section 12. Class suit. - When the subject matter of the controversy is one of common or general interest to many persons so numerous that it is impracticable to join all as parties, a number of them which the court finds to be sufficiently numerous and representative as to fully protect the interests of all concerned may sue or defend for the benefit of all. Any party in interest shall have the right to intervene to protect his individual interest. (12a)