(concurring).
I agree with the majority’s conclusion that appellants’ claim for compensatory damages is barred under the filed rate doctrine, but I disagree that appellants’ claim for injunctive relief is not barred under the filed rate doctrine. Because I conclude that the relevant provisions of the tariff are ambiguous, I would decline to answer the certified question as to whether the filed rate doctrine bars the claim for injunctive relief. I would simply refer appellants’ claim for injunctive relief to the Minnesota Public Utilities Commission (MPUC) to resolve the ambiguity in the tariff.
Like the majority, I conclude that the filed rate doctrine does not bar a claim for injunctive relief that merely seeks to enforce the terms of an existing tariff. See, e.g., Brown v. MCI WorldCom Network Servs., Inc., 277 F.3d 1166, 1171-72 (9th Cir.2002); Lipton v. MCI WorldCom, Inc., 135 F.Supp.2d 182, 189 (D.D.C.2001). *53Therefore, the dispositive issue here is whether appellants merely are seeking to enforce the terms of the tariff or whether they are seeking to add obligations to the tariff. The resolution of this issue depends on the scope of NSP’s maintenance obligation as set forth in the tariff, which requires interpretation of the tariff.
Courts typically interpret tariffs using the same principles as contract interpretation. See Carrier Serv., Inc. v. Boise Cascade Corp., 795 F.2d 640, 642 (8th Cir.1986). Unless ambiguous, the construction and effect of a contract constitutes a question of law. Denelsbeck v. Wells Fargo & Co., 666 N.W.2d 389, 346 (Minn.2003). The determination of whether a contract is ambiguous also constitutes a question of law. Id. “A contract is ambiguous if its language is reasonably susceptible to more than one interpretation.” Brookfield Trade Ctr., Inc. v. County of Ramsey, 584 N.W.2d 390, 394 (Minn.1998). When material contractual provisions are ambiguous, judgment on the pleadings is improper. See, e.g., Eternity Global Master Fund Ltd. v. Morgan Guar. Trust Co. of N.Y., 375 F.3d 168, 178 (2d Cir.2004); cf. In re Turners Crossroad Dev. Co., 277 N.W.2d 364, 368 (Minn.1979) (stating that if contractual terms at issue are ambiguous or uncertain, summary judgment is not appropriate).
The purpose of certification is to provide answers to important and doubtful legal questions. See Hawkins v. Thorp Credit & Thrift Co., 441 N.W.2d 470, 472 (Minn.1989) (explaining that the district court “must specify the precise legal question certified and make specific findings of fact” relevant to the certified question). Certification should not be used “to secure an advisory opinion.” Rude v. Rude, 283 Minn. 524, 525, 166 N.W.2d 719, 719 (1969) (per curiam). We consistently have declined to answer certified questions that are hypothetical or based on insufficient facts. Zobel & Dahl Constr. v. Crotty, 356 N.W.2d 42, 47 (Minn.1984); see, e.g., F. & H. Inv. Co. v. Sachman-Gilliland Corp., 305 Minn. 155, 158, 232 N.W.2d 769, 772 (1975); Staples v. Zinn, 302 Minn. 149, 152-53, 223 N.W.2d 415, 417-18 (1974).
The certified question here is: “Does the filed rate doctrine bar [appellants’] claims?” In considering whether the filed rate doctrine bars appellants’ claim for injunctive relief, the majority does not consider the threshold question of whether the tariff is ambiguous. Instead, the majority focuses on the standard of review for judgment on the pleadings. Construing the tariff provisions “in the light most favorable to appellants,” the majority concludes that “NSP must maintain certain equipment” and, therefore, that the filed rate doctrine does not bar the claim for injunctive relief.1
I disagree with the analysis of the majority. At this preliminary stage of the proceedings, appellants’ allegations in the complaint are only allegations. Because appellants and NSP offer different, reasonable interpretations of the tariff, I conclude that the tariff is ambiguous. In fact, in the section on primary jurisdiction, the majority agrees that the tariff is ambiguous and determines that the scope of NSP’s obligations under the tariff “is best suited for a first consideration by the MPUC.” As a result of the ambiguity, the *54certified question of-whether the claim for injunctive relief is barred by the filed rate doctrine is not ripe for determination by this court. I agree with the majority that the ambiguity in the tariff must first be resolved by the MPUC.
Under appellants’ interpretation of the tariff, the claim for injunctive relief can go forward; under NSP’s interpretation, the claim is barred by the filed rate doctrine. Consequently, the answer to the certified question depends on which of the two reasonable interpretations of the tariff will prevail. The majority attempts to sidestep this problem by assuming the allegations in the complaint are true. But appellants’ allegations ask this court to assume not only that the facts of the complaint are true, but also that the proposed interpretation of the ambiguous tariff will be the one adopted by the MPUC. Essentially, appellants seek an advisory opinion on whether the claim is barred by the filed rate doctrine if the MPUC accepts appellants’ proposed interpretation of the tariff. In short, the majority goes too far in answering the certified question based on appellants’ allegations in the complaint. See F. & H. Inv. Co., 305 Minn. at 158, 232 N.W.2d at 772 (stating that the court will not consider a certified question that “ ‘might result in one answer to one set of circumstances but another answer to a different set of circumstances.’ ” (quoting Thompson v. State, 284 Minn. 274, 277, 170 N.W.2d 101, 103 (1969))). Because the tariff is ambiguous, I would decline to answer the certified question and refer the interpretation of the tariff to the MPUC.
. In reviewing a ruling on a motion for judgment on the pleadings, we accept appellants’ factual allegations in the pleading as true. Lorix v. Crompton Corp., 736 N.W.2d 619, 623 (Minn.2007). We are not required to accept appellants’ allegations with respect to the construction of the tariff. See Int’l Audiotext Network, Inc. v. Am. Tel. & Tel. Co., 62 F.3d 69, 72 (2d Cir.1995) (but noting that courts "strive to resolve any contractual ambiguities" in favor of the nonmoving party in reviewing the dismissal of a complaint).