No. 96-1812 ARGUED OCTOBER 22, 1996 DECIDED DECEMBER 19, 1996 Aileen A. Armstrong, John Burgoyne (argued), National Labor Relations Board, Appellate Court, Enforcement Litigation, Washington DC, Joseph A. Szabo, Director, National Labor Relations Board, Region 30, Milwaukee, WI, for Petitioner. Paul D. Lawent (argued), Association of General Contractors of Wisconsin, Madison, WI, for Respondent. John J. Brennan (argued), Marianne G. Robbins, Previant, Goldberg, Uelmen, Gratz, Miller Bruegeman, Milwaukee