Buffalo Forge Co. v. United Steelworkers of America, 428 U.S. 397, 96 S.Ct. 3141, 49 L.Ed.2d 1022 (1976), made clear that Boys Markets, Inc. v. Retail Clerks Union Local 770, 398 U.S. 235, 90 S.Ct. 1583, 26 L.Ed.2d 199 (1970) authority to enjoin was limited to injunctions to enforce the union's promise to arbitrate. The strike involved in Buffalo Forge was a sympathy strike, not a strike over an arbitrable issue, and indeed the very applicability of the no-strike obligation was an arbitrable issue. Thus the federal courts could not enjoin the strike without intruding impermissibly into the merits of the dispute. "The parties have agreed to submit to grievance procedures and arbitrate, not to litigate," the Court said. "They have not contracted for a judicial preview of the facts and the law." Id. at 411, 96 S.Ct. at 3149.