42 U.S.C. § 304: Stopping payment on deviation from required provisions of plan or failure to comply therewith

that the plan has been so changed as to impose any age, residence, or citizenship requirement prohibited by section 302(b) of this title , or that in the administration of the plan any such prohibited requirement is imposed, with the knowledge of such State agency, in a substantial number of cases; or that in the administration of the plan there is a failure to comply substantially with any provision required by section 302(a) of this title to be included in the plan;