Every labor organization shall adopt a constitution and bylaws consistent with the provisions of the Act applicable thereto, within 90 days after the date the labor organization first becomes subject to the Act. This shall not, however, require the formal readoption by a labor organization of such a constitution and bylaws which it has previously adopted and under which it is operating when the report prescribed by § 402.2 is filed. As used in this part constitution and bylaws means the basic written rules governing the organization.