On April 1, 1976, J. E. D. entered into a collective bargaining agreement with Laborers Local 1140 and cancelled the said work permit with Local 571. Thereafter all forklift assignments were assigned to members of Laborers Local 1140. In a letter to J. E. D. the business agent for Local 571 disputed the work permit cancellation and forklift assignment to Laborers Local 1140. In May, 1976, Local 571 filed a jurisdictional work assignment complaint with the Impartial Jurisdictional Disputes Board in which it challenged J. E. D.'s forklift assignment to Laborers Local 1140 at the University of Nebraska job site and requested the reassignment of the forklift operations to Local 571. The Disputes Board notified J. E. D. of the complaint and the possibility of a violation of the procedural rules of the Disputes Board. J. E. D. denied the allegations and contended that the Disputes Board lacked jurisdiction over J. E. D. No further action followed.

In July, 1976, Local 571 requested payroll and other information from J. E. D. for collective bargaining and representation purposes. J. E. D. denied it had a collective bargaining agreement with Local 571 and repudiated the 1969 "Participation Agreements" because the forklift operations were assigned to Laborers Local 1140 pursuant to the collective bargaining agreement with J. E. D. Later in the year, Local 571 requested J. E. D. to attend a multi-employer meeting to negotiate changes in Local 571's "Building Agreement for Lancaster County, Nebraska." J. E. D. did not respond.

Local 571 filed a second jurisdictional work assignment complaint with the Disputes Board in July, 1977, in which it challenged J. E. D.'s forklift assignment to Laborers Local 1140 at the Millard warehouse job site. The Disputes Board notified J. E. D., which denied the allegations and the Disputes Board's authority over J. E. D.'s operations. Again, no further action followed.

In August, 1977, Local 571 advised J. E. D. by letter that although it did not purport to represent J. E. D.'s employees, it protested that the wage scale J. E. D. paid its employees who operated the forklift was below area standards. However, the Union did not protest the assignment of the forklift operations to the Laborers Local 1140.

In December, 1977, J. E. D. assigned forklift operations at the Southeast Community College work site to Laborers Local 1140. Due to inclement weather conditions, the forklift was used infrequently during the winter months. On March 10, 1978, continuous operation of the forklift resumed. Eleven days later Local 571 began picketing J. E. D. at the work site. The purpose of the picketing was allegedly to protest the lower wage scale paid by J. E. D. to members of Laborers Local 1140 who operated the forklift. As a consequence of the picketing, work on the construction site was curtailed.

On March 22, 1978, J. E. D. filed a complaint with the Regional Director of the NLRB. After its investigation, the NLRB, through the Regional Director, petitioned the District Court on April 5, 1978, for a Preliminary Injunction pursuant to § 10(L ) of the National Labor Relations Act. 29 U.S.C. § 160(L ). The NLRB alleged it had reasonable cause to believe the purpose of the picketing by Local 571 was to force J. E. D. to assign the forklift operations to members of Local 571, which was an unfair labor practice within the meaning of § 8(b)(4)(i)(ii)(D). 29 U.S.C. § 158(b)(4)(i)(ii)(D).3 The NLRB sought to enjoin further picketing by the Union for jurisdictional purposes until the final disposition by the NLRB of J. E. D.'s unfair labor practice complaint.

After an evidentiary hearing on April 21, 1978, the District Court found the factual allegations were substantial and the legal question was one of first impression, substantial and non-frivolous. Accordingly, the District Court concluded that the NLRB had reasonable cause to believe the picketing was an unfair labor practice and issued a Preliminary Injunction pursuant to § 10(L ).

On April 18, 1978, the NLRB held a § 10(k), 29 U.S.C. § 160(k),4 hearing to determine which Union was entitled to the forklift assignments. The Hearing Officer concluded that the Laborers Local 1140 was entitled to the assignments at J. E. D.'s present and future job sites in the Lincoln, Nebraska, area where the jurisdiction of the two unions coincided. On August 28, 1978, a Three Member Panel of the NLRB affirmed the decision of the Hearing Officer. International Union of Operating Engineers Local 571, AFL-CIO and J. E. D. Construction Co., Inc. and Laborers International Union of North America, Local 1140, AFL-CIO, 237 NLRB No. 125 (August 28, 1978).

The Norris-LaGuardia Act, 29 U.S.C. §§ 101-115, removed the jurisdiction of the Federal Courts to grant injunctive relief in labor disputes. 29 U.S.C. § 101.5 When Congress enacted the Taft-Hartley Act in 1947, 29 U.S.C. §§ 141-197, "it believed Norris-LaGuardia to be so broad that certain of the new provisions of section 8(b), creating union unfair labor practices, would be rendered nullities without some use of the injunctive process." McLeod v. Bus. Mach. and Off. App. Mech. Conf. Bd., Local 459, 300 F.2d 237, 240 (2d Cir. 1962). Further the crippling and destructive effects on commerce of the Section 8(b) unfair labor practices made time of the essence in enforcement proceedings.6 In addition,

(t)he relatively slow procedures of Board hearings and orders, followed many months later by an enforcing decree of the Circuit Court of Appeals, falls short of achieving the desired obligations of the prompt elimination of the obstacles to the free flow of commerce and encouragement of the practice and procedure of free and private collective bargaining.

Sen.Rep.No.105, 80th Cong., 1st Sess. 7-8, Reprinted in I NLRB, Legislative History of the Labor Management Relations Act, 1947, at 433 (1948). See Muniz v. Hoffman, 422 U.S. 454, 466-67, 95 S. Ct. 2178, 45 L. Ed. 2d 319 (1975); Dawidoff v. Minn. Bldg. and Const. T. C., 550 F.2d 407, 412 (8th Cir. 1977).7 The solution of this dilemma was further complicated by the underlying Congressional intent in the Labor Act that the NLRB make the primary findings of fact and interpretations of the statutory scheme of the Labor Act.8 Squillacote v. Inter. Broth. of Teamsters, Local 344, 561 F.2d 31, 33-35 (7th Cir. 1977); Dawidoff v. Minn. Bldg. and Const. T. C., supra, 550 F.2d at 412-13; McLeod v. Natl. Maritime Union of America, AFL-CIO, 457 F.2d 490, 494 (2d Cir. 1972).

Congress resolved these various considerations by enacting Section 10(L ). 29 U.S.C. § 160(L ).9 In order to insure prompt and effective action, Section 10(L ) empowers the Federal District Courts to issue appropriate injunctive relief when it finds reasonable cause to believe that an unfair labor practice occurred. The injunction preserves the status quo pending a full and final adjudication by the Board of the unfair labor practice charges. Sears, Roebuck & Co. v. Carpet Linoleum, Soft Tile & Resilient Floor Covering Layers Local Union 419, AFL-CIO, 397 U.S. 655, 658-59, 90 S. Ct. 1299, 25 L. Ed. 2d 637 (1970); Kaynard v. Local 282 Inter. Broth. of Teamsters, 576 F.2d 471, 479 (2d Cir. 1978); Hirsch v. Bldg. and Const. T. C., 530 F.2d 298, 302 (3d Cir. 1976); NLRB v. Queen Mary Rest. Corp., 522 F.2d 6, 7 (9th Cir. 1975). In addition, the section 10(L ) injunction forestalls the use of economic coercion to resolve the labor dispute and preserves the Board's jurisdiction so that the ultimate decision of the Board will not be negated, nullified or rendered moot by the intervening events.10 Compton v. Nat. Maritime Union of America, AFL-CIO, 533 F.2d 1270, 1276 (1st Cir. 1976); Squillacote v. Graphic Arts Inter. Union, Local 277, supra, 513 F.2d at 1020; Samoff v. Bldg. and Const. T. C., 475 F.2d 203, 207 n.6 (3d Cir. 1973). See also Dawidoff v. Minn. Bldg. and Const. T. C., supra, 550 F.2d at 412; Hirsch v. Bldg. and Const. T. C., supra, 530 F.2d at 302.

The decision making process of the District Court in a Section 10(L ) injunction proceeding is twofold. In the first instance the District Court is not called upon to decide whether an unfair labor practice occurred, but rather, after deferring to the statutory interpretation and rational factual inferences of the Board, Danielson v. Inter. Organ. of Masters, Mates and Pilots, AFL-CIO, 521 F.2d 747, 751 (2d Cir. 1975); Squillacote v. Graphic Arts Inter. Union, Local 277, supra, 540 F.2d at 858, the district court must decide whether there is reasonable cause11 to believe that an unfair practice occurred. Dawidoff v. Minn. Bldg. & Const. T. C.,supra, 550 F.2d at 410-11; Wilson v. Milk Drivers and Dairy Employees Union, Local 471, 491 F.2d 200, 203 (8th Cir. 1974); Local Joint Bd., Hotel & Rest. Employees and Bartenders Inter. Union v. Sperry, 323 F.2d 75, 77-78 (8th Cir. 1963). In addition the District Court must be satisfied the legal issues are "substantial and non-frivolous." Local Joint Bd., Hotel & Rest. Employees and Bartenders Inter. Union v. Sperry, supra, 323 F.2d at 77-78.12 Since the Board must establish only the substantiality of the legal theory and not its ultimate validity, a novel or untested legal theory is not necessarily non-substantial. Squillacote v. Graphic Arts Inter. Union, AFL-CIO, supra, 540 F.2d at 859; Eisenberg v. Hartz Mtn. Corp.,519 F.2d 138, 141 n.2 (3d Cir. 1975); Hirsch v. Bldg. and Const. T. C. of Phil., supra, 530 F.2d at 302; Boire v. Inter. Broth. of Teamsters, 479 F.2d 778, 789 (5th Cir. 1973) (10(j) proceeding).13

In the second instance, if the District Court finds reasonable cause to believe that an unfair labor practice occurred, it must then decide whether equitable relief is "just and proper." In addition to the usual discretionary considerations, the district court must consider whether the statutory purpose of the Section 10(L ) remedy would be frustrated if injunctive relief was denied. Wilson v. Milk Drivers and Dairy Employees Union, supra, 491 F.2d at 203; Minn. Mining and Mfg. Co. v. Meter, 385 F.2d 265, 270-72 (8th Cir. 1967).

The scope of appellate review of a Section 10(L ) proceeding

is limited to a determination of whether the trial court's finding that there is reasonable cause to believe that a violation of the Act charged has been committed is clearly erroneous and whether the trial court abused its discretion in granting injunctive relief.

Local Joint Bd. Hotel and Rest. Employees and Bartenders Union v. Sperry, supra, 323 F.2d at 77. See Dawidoff v. Minn. Bldg. and T. C., supra, 550 F.2d at 412.

The undisputed facts of this case establish a history of disagreement between J. E. D. and Local 571 about the work assignment of the forklift operations. The Union's letters to J. E. D. and complaints to the Impartial Jurisdictional Disputes Board demonstrate the Union's claim of the forklift operations for its members. Although the Union claimed it had abandoned this dispute, the District Court found that the Union's primary motivation for the March 21, 1978, picketing was the Union's continuing demand for the forklift assignments and not solely a demand for adherence to area wage standards. After a thorough review of the record, we cannot say the District Court's finding of reasonable cause is clearly erroneous.

However, the resolution of the reasonable cause question does not end our task, since the Union contends that, in view of Section 10(b),14 it was reversible error for the District Court to receive and consider the evidence of events which occurred prior to the six month period preceding the March 21, 1978, picketing. The dispositive nature of this issue was noted by District Court:

I conclude that the only evidence of acts occurring within the six-month period is insufficient to support a determination of reasonable cause to believe that the charge is true, but that if evidence of acts which occurred during the months immediately preceding the six-month limitations period is considered, the reasonable cause determination is supportable.

The leading case construing Section 10(b) is Local Lodge No. 1424, Inter. Assn. of Machinists, AFL-CIO v. NLRB, 362 U.S. 411, 80 S. Ct. 822, 4 L. Ed. 2d 832 (1960), in which the Supreme Court recognized two distinguishable circumstances when applying rules of evidence as to the admissibility of past events.

It is doubtless true that § 10(b) does not prevent all use of evidence relating to events transpiring more than six months before the filing and service of an unfair labor practice charge. However, in applying rules of evidence as to the admissibility of past events, due regard for the purposes of § 10(b) requires that two different kinds of situations be distinguished. The first is one where occurrences within the six-month limitations period in and of themselves may constitute, as a substantive matter, unfair labor practices. There, earlier events may be utilized to shed light on the true character of matters occurring within the limitations period; and for that purpose § 10(b) ordinarily does not bar such evidentiary use of anterior events. The second situation is that where conduct occurring within the limitations period can be charged to be an unfair labor practice only through reliance on an earlier unfair labor practice. There the use of the earlier unfair labor practice is not merely 'evidentiary,' since it does not simply lay bare a putative current unfair labor practice. Rather, it serves to cloak with illegality that which was otherwise lawful. And where a complaint based upon that earlier event is time-barred, to permit the event itself to be so used in effect results in reviving a legally defunct unfair labor practice.

363 U.S. at 416-17, 80 S. Ct. at 826.

The consideration of events outside the six-month period depends upon the gravamen of the unfair labor practice complaint. Machinist Local 1424, supra, 362 U.S. at 419-420, 80 S. Ct. 822; NLRB v. Auto Warehousers, Inc., 571 F.2d 860, 863-64 (5th Cir. 1978); NLRB v. R. L. Sweet Lumber Co., 515 F.2d 785, 790-92 (10th Cir. 1975). If the Trial Court merely uses the anterior events in an evidentiary or background manner, the consideration of the events is proper. If, however, the events are used to resurrect a defunct or stale unfair labor practice charge, Section 10(b) bars the consideration of the events.15 NLRB v. Auto Warehousers, Inc., supra, 571 F.2d at 863-64; Queen Mary Rest. Corp. v. NLRB, supra, 560 F.2d at 407 n.2; NLRB v. R. L. Sweet Lumber Co., supra, 515 F.2d at 790-92.

As the District Court noted, the present case is comparable to the first situation in Machinist Local 1424. However, in Machinist Local 1424 the Supreme Court discussed, but did not resolve, a third situation, which more closely resembles the facts in this appeal.

(S)ome Board cases have gone even further and held § 10(b) a bar in circumstances when, although none of the material elements of the charge in a timely complaint need necessarily be proved through reference to the barred period so that utilization of evidence from that period is ostensibly only for the purpose of giving color to what is involved in the complaint yet the evidence in fact marshalled from within the six-month period is not substantial, and the merit of the allegations in the complaint is shown largely by reliance on the earlier events. See, e. g., News Printing Co., 116 N.L.R.B. 210, 212; Universal Oil Products Co., 108 N.L.R.B. 68; Tennessee Knitting Mills, Inc., 88 N.L.R.B. 1103. However, we express no view on the problem raised by such cases . . . .

362 U.S. at 421-22, 80 S. Ct. at 829.

The Supreme Court has not resolved the questions raised by the third situation, and the two circuits which have considered the third situation have reached different conclusions.16

The present posture of this appeal does not require a resolution of the question raised in the third situation of Machinist Local 1424. Nor is this Court called upon to place the present factual pattern in the first, second or third situation. The initial determination of these issues is reserved exclusively for the Board subject to judicial review under § 10(e), (f). The District Court's injunction merely preserves the status quo until the Board holds a full hearing on the factual and legal issues. It is sufficient in a Section 10(L ) proceeding that the factual allegations and legal issues are substantial and non-frivolous, albeit novel and untested. The lack of a clear resolution of the issues raised by the third situation in Machinist Local 1424 demonstrates the need to allow the Board the initial opportunity to apply its expertise to the issues in this case. Accordingly, the District Court's findings of substantial legal issues and reasonable cause to believe an unfair practice occurred are not clearly erroneous.

On this appeal the Union argues, and the Board concedes,17 that the scope of the preliminary injunction is overbroad in that the Union is enjoined from picketing J. E. D. "for any purpose."18 Since the Section 10(L ) injunction is a statutory exception to the Norris-LaGuardia Act, 29 U.S.C. § 101, which denied equitable jurisdiction to Federal District Courts in labor disputes, it should be limited to the narrow jurisdiction of Section 10(L ). Compton v. Nat. Maritime Union of America, 533 F.2d 1270, 1276 (1st Cir. 1976); Eisenberg v. Hartz Mtn. Corp., 519 F.2d 138, 141-42 (3d Cir. 1975). See also McLeod v. Bus. Mach. & Off. App. Mech. Conf. Bd., supra,300 F.2d at 239-41. Therefore, a Section 10(L ) injunction may enjoin only those unlawful labor practices specified in the Labor Act. Potter v. Houston Gulf Coast Bldg., T. C., 482 F.2d 833, 840-41 (5th Cir. 1973); McLeod v. Chefs, Cooks, Pastry Cooks, Local 89, 280 F.2d 760, 763-64 (2d Cir. 1960). See also Youngdahl v. Rainfair, Inc., 355 U.S. 131, 78 S. Ct. 206, 2 L. Ed. 2d 151 (1960). Accordingly, an injunction against the Union from picketing "for any purpose" goes beyond the narrow limits of Section 10(L ).

The final argument of the Union is that the time span of the injunction should not continue in force until final Board action, but rather it should be limited to a definite time. We find the congressional history indicates that Congress was aware of the lengthy Board hearing procedures when Section 10(L ) was enacted. Since Congress did not impose a time limit on a Section 10(L ) injunction, we find no reason why this Court should impose such a limit.19

The Order of the District Court is affirmed, but remanded with directions to modify its injunctive order by limiting the scope of the Order consistent with this opinion.