Vacated and remanded by published opinion. Judge HAMILTON wrote the opinion, in which Judge NIEMEYER and Chief Judge BOYLE joined.
OPINION
Under the Railway Labor Act (RLA), 45 U.S.C. §§ 151-188, federal district courts have subject-matter jurisdiction over “major disputes” in railway labor relations, but lack jurisdiction over “minor disputes.”
See Consolidated Rail Corp. v. Railway Labor Executives’ Ass’n,
In this case, the South Carolina Public Kailway Commission (Railway Commission) asserts that the district court lacked subject-matter jurisdiction to issue a preliminary injunction requiring the Railway Commission to pay rate-of-pay increases, lump sum payments, and health and welfare adjustments contained in a national collective bargaining agreement, because its dispute with the United Transportation Union (the Union) is a minor one. We agree with the Railway Commission that its dispute with the Union is fundamentally a dispute seeking to enforce contractual rights and is, therefore, a minor dispute under the RLA. Consequently, we vacate the prehminary injunction and remand the case with instructions to dismiss for lack of subject matter jurisdiction.
I.
A.
Collective bargaining in the railroad industry is conducted on both the national and local levels. Local collective bargaining involves negotiations between a single employer and an individual union, whereas national collective bargaining (commonly referred to as “national handling”) involves multiple employers and multiple unions. Unions and employers typically participate in national bargaining by conferring their bargaining authority to multi-union and multi-carrier bargaining agents. These agents then negotiate a single national agreement which is binding on all the parties.
See United Transportation Union v. Illinois Cent. R.R. Co.,
Collective bargaining in the railroad industry, on both the national and local levels, is covered by the RLA, 45 U.S.C. § 151-188. In
Detroit & Toledo Shore Line R.R. v. United Transp. Union,
The Railway Labor Act was passed in 1926 to encourage collective bargaining by railroads and their employees in order to prevent, if possible, wasteful strikes and interruptions of interstate commerce. The problem of strikes was considered to be particularly acute in the area of “major disputes,” those disputes involving the formation of collective agreements and efforts to change them. Rather than rely upon compulsory arbitration, to which both sides were bitterly opposed, the railroad and union representatives who drafted the Act chose to leave the settlement of major disputes entirely to the processes of non-compulsory adjustment. To this end, the Act established rather elaborate machinery for negotiation, mediation, voluntary arbitration, and conciliation. It imposed upon the parties an obligation to make every reasonable effort to negotiate a settlement and to refrain from altering the status quo by resorting to self-help while the Act’s remedies were being, exhausted.
Id.
at 148-49,
Another railroad-industry practice that influenced the RLA was that of negotiating open-ended agreements. Railroad collective bargaining agreements do not expire on a given date but remain in effect until one party proposes modifications of the agreement, whereupon a new round of negotiations takes place. When the parties conclude an agreement on those issues, the contract is modified accordingly.
See Trans World Airlines v. Independent Fed’n of Flight Attendants,
Section 6 requires employers and unions to give the other party a 30-day notice of proposed changes in agreements affecting rates of pay, rules, or working conditions.
See id.
*629
The filing of a Section 6 notice commences a period of mandatory negotiation, during which the existing rates of pay, rules and working conditions generally may not be altered until the controversy is resolved.
See id.
If the parties cannot agree between themselves, the negotiations then go to mediation, usually under the auspices of the National Mediation Board.
See
45 U.S.C. § 155. Sometimes, it becomes necessary for the President to appoint an Emergency Board to make a report and recommendations to resolve the dispute.
See
45 U.S.C. § 160.
See also Detroit & Toledo Shore Line,
In summary, neither party may change the
status quo
with respect to existing agreements without first filing a Section 6 notice, and must maintain the
status quo
until the collective bargaining process is complete.
See Detroit & Toledo Shore Line,
B.
The Railway Commission is an agency of the State of South Carolina which operates a railroad that transports goods in interstate commerce. The Railway Commission is therefore a rail “carrier” as defined by the RLA. See 45 U.S.C. § 151 First. The Union is an unincorporated labor organization which represents railroad employees throughout the United States and Canada. Consequently, the Union is a “representative” under the RLA. See 45 U.S.C. § 151 Sixth. The Union represents employees of the Railway Commission.
On July 2, 1973, the Union and Railway Commission completed a round of local collective bargaining and signed into effect an “Agreement Between The South Carolina Public Railways [sic] Commission and its Yard Employees Represented by United Transportation Union” (the 1973 Agreement). (J.A. 24). Article 42 provides that the agreement would “become effective as of July 2, 1973 and remain in effect until changed in accordance with the provisions of the Railway Labor Act, amended.” (J.A. 27). Two other provisions of that agreement are in dispute in this case:
Article 1. Rates of pay:
(a) Rates of pay will be governed by those agreed upon by the national agreement.
Article SJp. Health and welfare:
(a) The national Health and Welfare Agreement consummated between the Carriers Conference Committee and the United Transportation Union, subject to any extensions or modifications by constituted authority of the United Transportation Union, is part of this agreement.
(J.A. 25-26).
The two national agreements which Articles 1(a) and 34(a) incorporate had been previously negotiated and were in force at the time the 1973 Agreement was enacted. However, in January 1977, August 1977, February 1981, and July 1988, the Union triggered new rounds of national handling by serving Section 6 notices on “practically all railroads in the United States,” which notices expressed a desire to change existing agreements. (See J.A. 28-31). In each instance, the Railway Commission chose not to participate in the national handling. Instead, the Railway Commission and the Union enacted local “standby agreements” that adopted the terms of the national agreements when they were finalized. 1 All these standby agree *630 ments are essentially identical in wording, and provide in their entirety:
In accordance with provisions of the Railway Labor Act, as amended, a notice was served under date of [date differed for each standby agreement], on practically all rail-roads in the United States, including [the South Carolina Public Railway Commission], by the accredited representative of employees of such railroads who are represented by the United Transportation Union, of a desire to change existing agreements as set forth in an attachment made part of the aforesaid notice.
The management of [the South Carolina Public Railway Commission] has not authorized and will not authorize any of the conference committees selected by the railroads to represent it in the handling of these matters. Therefore, it is hereby agreed between the SC Public Railways Comm. Railroad and the accredited representative of the employees involved, signatories hereto, that any settlement or disposition of these matters reached through national handling shall be adopted and applied by the said SC Public Railways Comm. Railroad and the employees involved in the same manner and made effective as of the same date as it is adopted and applied on the railroads, parties to such national handling.
(J.A. 31) (emphasis added). In each ease, when the Union served its Section 6 notices on the Railway Commission regarding the national handling, the Union enclosed a proposed standby agreement.
When the contract moratorium covered by the 1988 Standby Agreement expired in 1995, the Union and the Railway Commission served Section 6 notices on each other, requesting changes in various aspects of compensation and working conditions. In its notice, the Railway Commission stated it would not enter into another standby agreement as it had previously. Instead, the Railway Commission preferred to negotiate wage and benefits locally.
On May 8, 1996, a new national agreement was finalized. As in the case of all previous national handling, the Railway Commission was not a party to the national agreement. In a letter dated May 22, 1996, the Union requested that, pursuant to Articles 1(a) and 34(a) of the 1973 Agreement, the Railway Commission implement the rates of pay, lump-sum payments and health and welfare benefits contained in the 1996 national agreement. On June 11, 1996, the Railway Commission responded that the existing rates of pay would remain unchanged. The Railway Commission stated that its 1995 Section 6 notice served notice upon the Union that the compensation elements were to be negotiated, and that the Railway Commission had not agreed to be bound by the national agreement. After an additional exchange of correspondence between the parties, the Union brought this action seeking declaratory and injunctive relief under the RLA to force the Railway Commission to apply the pay, health and welfare provisions of the 1996 national agreement.
In the district court, the Union moved for a preliminary
status quo
injunction against the Railway Commission, and the Railway Commission moved to dismiss. The Railway Commission argued that the dispute was a “minor dispute” under the RLA and subject to mandatory arbitration. Accordingly, the Railway Commission argued that the district court lacked subject-matter jurisdiction to hear the dispute.
See Consolidated Rail,
In considering the parties’ motions, the district court assessed whether the dispute was a “major dispute” or “minor dispute” under the RLA. The district court rejected the Railway Commission’s suggestion that the parties’ “past practice” of entering into standby agreements was evidence that the 1973 Agreement was not intended to incorporate the terms of all future national agreements. Instead, the district court found the 1973 Agreement to unambiguously adopt the terms of all national agreements. The district court concluded that the Railway Commission’s position was “not arguable” and, therefore, the dispute was a “major dispute.”
See id.
at 305-07,
II.
A.
We review the grant of a preliminary injunction for abuse of discretion.
See Manning v. Hunt,
B.
The key question at issue in this appeal is whether the parties’ dispute is “major” or “minor” under the RLA. The answer to this question determines whether the district court had subject-matter jurisdiction to hear the case.
See Consolidated Rail,
The RLA does not explicitly use the terms “major dispute” or “minor dispute.” Rather, these are terms adopted by the courts from the vocabulary of railroad management and labor as a shorthand method of describing two classes of controversies Congress had distinguished in the RLA. As we will explain more fully below, “major disputes” seek to create contractual rights, while “minor disputes” seek to enforce those rights.
See id.
at 302,
The statutory basis of the major dispute category is found in § 2 Seventh and § 6 of the RLA, 45 U.S.C. § 152 Seventh and § 156. The former states that “No carrier, its officers or agents shall change the rates of pay, rules, or working conditions of its employees, as a class as embodied in agreements except in the manner prescribed in such agreements” or through the mediation procedures established in RLA § 6.
See Consolidated Rail,
Minor disputes, on the other hand, are based on RLA § 2 Sixth and § 3 First (i), 45 U.S.C. §§ 152 Sixth and 153 First (i). These sections establish conference and compulsory arbitration procedures for disputes arising out of “grievances or out of the interpretation or application of agreements concerning rates of pay, rules, or working conditions.”
Id.
§ 152 Sixth.
See Consolidated Rail,
The difficulty is, of course, determining whether any given dispute is a major or minor one. In
Consolidated Rail,
the Supreme Court addressed the standard for differentiating between the two,
see id.
at 300,
disputes over the formation of collective agreements or efforts to secure them. They arise where there is no such agreement or where it is sought to change the terms of one, and therefore the issue is not whether an existing agreement controls the controversy. They look to the acquisition of rights for the future, not to assertion of rights claimed to have vested in the past.
Id.
at 302,
contemplate! ] the existence of a collective agreement already concluded or, at any rate, a situation in which no effort is made to bring about a formal change in terms or to create a new one. The dispute relates either to the meaning or proper application of a particular provision ... or to an omitted case.... In either case the claim is to rights accrued, not merely to have new ones created for the future.
Id.
at 303,
The Supreme Court concluded that the demarcation between major and minor disputes is, therefore, neither the importance of the issue nor the likelihood one party would resort to self-help. Instead, the line drawn is whether one of the parties asserts that the terms of an existing agreement either establishes or refutes the presence of a right to take the disputed action. “The distinguishing feature of such a case is that
the dispute may be conclusively resolved by interpreting the existing agreement.” Id.
at 305,
The test the Supreme Court therefore creates in
Consolidated Rail
is that “[w]here [a party] asserts a contractual right to take the contested action, the ensuing dispute is minor....”
Id.
at 307,
The Supreme Court stated that the railroad has the burden of establishing the exclusive arbitral jurisdiction under the RLA (and, consequently, the lack of jurisdiction in the district court), but added that the railroad’s burden is “relatively light.”
Id.
at 307,
[a] district court need not, indeed should not, assess the relative merits of the parties’ competing interpretations of the contract in order to find the dispute “minor.” If the railroad’s assertion that the collective bargaining agreement controls the dispute rises above the “frivolous or obviously insubstantial,” then the court must dismiss the action for lack of subject matter jurisdiction.
Id.
Finally, as the Supreme Court noted in
Consolidated Rail,
although the union’s interpretation could conceivably carry the day in arbitration, that does not mean that the railroad’s contractual interpretation is frivolous or insubstantial.
See Consolidated Rail,
*633 C.
Applying the above rules to the facts of this case, we must decide whether the Railway Commission’s position is “arguably justified by the terms of the parties’ collective-bargaining agreement” or, rather, “frivolous or obviously insubstantial.”
See Consolidated Rail,
The
Consolidated Rail
Court held that “[tjhe distinguishing feature of [a minor dispute] is that the dispute may be conclusively resolved by interpreting the existing agreement.”
Id.
at 305,
In reality, the district court’s decision turned entirely on the interpretation of the 1973 Agreement and standby agreements. The district court examined the provisions of all these local agreements and the parties’ alleged past practices, and found that the Railway Commission’s interpretation was not arguable. Consequently, the district court concluded that the Railway Commission was attempting to unilaterally alter the terms of the 1973 Agreement, constituting a major dispute. This demonstrates that even the district court implicitly recognized that this dispute was fundamentally about contract interpretation. However, we believe the district court erred in concluding the Railway Commission’s interpretation was not arguable.
Examining the facts of this case, we believe the Railway Commission’s position is “arguably justifiable” in light of the 1973
*634
Agreement and the standby agreements and, therefore, the Railway Commission has met its light burden of establishing exclusive arbi-tral jurisdiction.
See id.
at 307,
However, in response to questions at oral argument, counsel for the Union maintained it was entirely proper for the 1973 Agreement to refer to
the
national agreement. Counsel argued that, since collective bargaining agreements under the RLA never expire but are modified only after Section 6 notice and negotiations, there is in reality only one national agreement. Although this argument could conceivably carry the day in arbitration, it only serves to further emphasize that the parties dispute the meaning of the 1973 Agreement. It does not, however, do anything to convince us that it is “frivolous or obviously insubstantial” for the Railway Commission to interpret “the national agreement” as being a particular agreement in effect or under consideration at the time.
See id.
at 317,
Moreover, the record clearly shows that the parties used standby agreements for
every
subsequent round of national handling. If the 1973 Agreement truly incorporates all future national agreements, each of these standby agreements would be superfluous. If, on the other hand, the 1973 Agreement only incorporated the national agreement in effect at the time, each subsequent standby agreement would have been
necessary
in order to adopt subsequent national agreements. The record clearly shows it was the Union that instigated adoption of each standby agreement. Although not determinative, these facts are evidence that the parties’ past practice was to incorporate new national agreements only through standby agreements, rather than automatic incorporation into the 1973 Agreement.
See generally, id.
at 311-20,
Next, the first paragraph and the first sentence of the second paragraph of each standby agreement explains the purpose of the standby agreement:
*635 In accordance with provisions of the Railway Labor Act, as amended, a notice was served under date of [date differed for each Standby agreement], on practically all rail-roads in the United States, including [the South Carolina Public Railway Commission], by the accredited representative of employees of such railroads who are represented by the United Transportation Union, of a desire to change existing agreements as set forth in an attachment made part of the aforesaid notice.
The management of [the South Carolina Public Railway Commission] has not authorized and will not authorize any of the conference committees selected by the railroads to represent it in the handling of these matters. Therefore, it is hereby agreed [that the national agreement will be adopted by the parties],
(J.A. 28-31). These provisions, contained in every standby agreement (and entirely ignored by the district court in its order), clearly explain that: (1) the Railway Commission was not a party to the national handling; and (2) the Railway Commission did not merely acquiesce to the results of the national handling, but specifically agreed to adopt that particular national agreement. This is additional evidence of the parties’ past practice which the district court should have considered in interpreting the terms of the parties’ agreement.
See Consolidated Rail,
Finally, the record shows that the Union has admitted the standby agreements were the parties’ usual practice. When the Union initiated the process leading up to the 1988 Standby Agreement, the Union’s General Chairperson, John W. Coulter, stated in a letter to the Railway Commission that “[t]he standby agreement has always been the norm concerning our seniority, work rules and rates of pay.” (J.A. 32). He went on to explain why that was the case: “This agreement is in alignment with South Carolina State Law 54-3-210 which provides for our work rules and rates of pay to be'in force relative to like employees of interstate railroads operating in the same territory with the terminal railroads authorized hereby.’” (J.A. 32) (emphasis added). In other words, instead of merely accepting the national agreement, the parties left open the possibility of agreeing locally to more regional rates and rules.
The district court, relying on
United Transp. Union v. Gateway W. Ry.,
No. 95-0908-CV-W-1,
This conclusion may well result in a delay of the bargaining process between the Railway Commission and the Union until the arbitration process has interpreted the 1973 Agreement and the standby agreements. Nevertheless, the Supreme Court has explicitly allowed such a consequence to occur. The Consolidated Rail Court stated:
The effect of this ruling, of course, will be to delay collective bargaining in some cases until the arbitration process is exhausted. But we see no inconsistency between that result and the policies of the RLA. In most cases where the Board determines that the employer’s conduct was *636 not justified by the contract, the Board will be able to fashion an appropriate compensatory remedy which takes account of the delay.
Consolidated Rail,
III.
Because we conclude that the present dispute is a “minor dispute” under the RLA, we hold that the district court abused its discretion in issuing the preliminary injunction against the Railway Commission.
See McHan,
VACATED AND REMANDED.
Notes
. In 1988, the Railway Commission first declined to enter into a standby agreement with the Union, wishing instead to negotiate locally rather than accept the national agreement. The Railway Commission later changed its mind and entered into a standby agreement on August 9, 1988. The 1988 Standby Agreement incorporated the national agreement that was finally completed in 1991.
. At oral argument, we granted the Railway Commission’s motion for a stay of the district court’s injunction pending the outcome of this appeal.
. Counsel for the Union admitted at oral argument they are seeking to enforce the existing contract, not to form a new agreement. However, counsel still characterized the case as a major dispute because the Union was seeking to maintain the
status quo.
In so arguing, counsel cited to the Supreme Court’s decision in
Detroit & Toledo Shore Line v. United Transportation Union,
The Union’s argument merely begs the question.
If
the dispute is a major dispute, then the parties are obligated to "preserve and maintain unchanged those actual, objective working conditions and practices, broadly conceived, which were in effect prior to the time the pending dispute arose and which are involved in or related to that dispute.”
See id.
at 153,
. In other words, we believe the parties would have more naturally stated in Article 1(a) of 1973 Agreement words to the effect that "Rates of pay will be governed by those agreed upon by national agreements." (Compare J.A. 25). Furthermore, in Article 34(a) the parties would have naturally stated that "National Health and Welfare Agreements to be consummated between the [parties] ... are a part of this agreement." (iCompare J.A. 26).
. Because of our disposition of the case on this issue, we need not reach the other issue the Railway Commission raises in its appeal, namely whether the district court's injunction deprives the Railway Commission of selecting its own bargaining representatives.
