No. 80-1501. Argued May 14, 1981. Decided June 15, 1982. Joseph Semo, Washington, D.C., with whom Ira M. Lechner, Washington, D.C., was on the brief, for appellants. William T. Torgerson, Washington, D.C., with whom John J. Ross and Wendy T. Kirby, Washington, D.C., were on the brief, for appellee. Gerald M. Feder, Robert J. Connerton and Theodore T. Green, Washington, D.C., were on the brief for amicus curiae, Nat. Coordinating Committee for Multiemployer Plans, urging reversal. Laurence J. Cohen