Congress enacted the FCUA in 1934 authorizing the chartering of credit unions at the national level and provided that federal credit unions at the national level may as a general matter offer banking services only to their members. Section 109 expressly restricts membership in federal credit unions. In 1982, the NCUA (D) has interpreted section 109 to permit federal credit unions to be composed of multiple unrelated employer groups, each having its own common bond of occupation. First National Bank & Trust (R) and others have challenged that interpretation on the ground that section 109 unambiguously requires the same common bond of occupation unite every member or an occupationally defined federal credit union. Under the new NCUA interpretation, each employer group must be located within an area surrounding the credit union as determined by the NCUA. After the new 1982 ruling, AT&T Family Federal Credit Union (ATTF) expanded its operations by adding unrelated groups to its membership only 35% of who were employees of AT&T and its affiliates. First (Ps) brought this action in 1990 after the NCUA allowed a series of amendments to ATTF's charter.