ORDER DENYING WITHOUT PREJUDICE DEFENDANT’S MOTION TO COMPEL ARBITRATION; GRANTING IN PART DEFENDANT’S MOTION TO DISMISS

*892 I. INTRODUCTION

Plaintiffs 1 bring this putative class action against Apple, Inc. (“Defendant”) alleging violations of Section 2 of the Sherman Act, 15 U.S.C. § 2 . Plaintiffs allege that Defendant violated the Sherman Act by conspiring with non-party AT & T Mobility, LLC (“ATTM”) to monopolize an alleged aftermarket for voice and data services for iPhones, and also by monopolizing or attempting to monopolize an alleged aftermarket for software applications for iPhones.

Presently before the Court are Defendant’s Motion to Compel Arbitration 2 and Motion to Dismiss. 3 The Court conducted a hearing on June 18, 2012. Based on the papers submitted to date and oral argument, the Court DENIES without prejudice Defendant’s Motion to Compel Arbitration and GRANTS in part Defendant’s Motion to Dismiss.

II. BACKGROUND A. Factual Allegations

In a Consolidated Class Action Complaint 4 filed on March 21, 2012, Plaintiffs allege as follows:

On the basis of the allegations outlined above, Plaintiffs assert three causes of action: (1) Unlawful Monopolization of the Applications Aftermarket, in Violation of Section 2 of the Sherman Act; (2) Attempted Monopolization of the Applications Aftermarket, in Violation of Section 2 of the Sherman Act; and (3) Conspiracy to Monopolize the iPhone Voice and Data Services Aftermarket, in Violation of Section 2 of the Sherman Act.

B. Procedural History

On December 29, 2011, Robert Pepper, Stephen H. Schwartz, Edward W. Hayter and Harry Bass (collectively, “Pepper Plaintiffs”) filed a Class Action Complaint. (See Docket Item No. 1.) The Pepper Plaintiffs are represented by Wolf Haldenstein. (Id.) On January 17, 2012, Eric Terrell, James Blackwell and Crystal Boy-kin (collectively, “Terrell Plaintiffs”) filed a substantially identical Class Action Complaint. 6 The Terrell Plaintiffs were represented by the Terrell Law Group. (Id.) On March 20, 2012, the Court ordered that the two cases be consolidated. 7 On March 21, 2012, Plaintiffs filed their Consolidated Class Action Complaint. (See Complaint.) *894 On March 29, 2012, the Court issued an order requesting motions for appointment of interim class counsel. 8 On April 9, 2012, 2012 WL 1514828 , on the basis of its finding that Wolf Haldenstein could adequately represent the interests of the class, and insofar as no other representative sought appointment as class counsel, the Court appointed Wolf Haldenstein as class counsel. 9

Presently before the Court are Defendant’s Motion to Compel Arbitration and Motion to Dismiss.

III. STANDARDS A. Motion to Compel Arbitration

It is fundamental that “a party cannot be required to submit to arbitration any dispute which [it] has not agreed so to submit.” Samson v. NAMA Holdings, LLC, 637 F.3d 915, 923 (9th Cir. 2011) (citations omitted). However, it is also well established that “[a]rbitration provides a forum for resolving disputes more expeditiously and with greater flexibility than litigation.” Lifescan, Inc. v. Premier Diabetic Servs., Inc., 363 F.3d 1010, 1011 (9th Cir.2004) (citation omitted). Congress created the Federal Arbitration Act (“FAA”) to “overrule the judiciary’s longstanding refusal to enforce agreements to arbitrate ... and place such agreements on the same footing as other contracts.” Id. (citation omitted). “A party to a valid arbitration agreement may ‘petition any United States district court for an order directing that such arbitration proceed in the manner provided for in such agreement.’” Id. at 1012 (quoting 9 U.S.C. § 4 ). The district court’s “role is limited to determining whether a valid arbitration agreement exists and, if so, whether the agreement encompasses the dispute at issue.” See id.; see also Chiron Corp. v. Ortho Diagnostic Sys., Inc., 207 F.3d 1126, 1130 (9th Cir.2000). A court interpreting the scope of an arbitration provision should apply ordinary state law principles of contract construction. See First Options of Chicago, Inc. v. Kaplan, 514 U.S. 938, 944 , 115 S.Ct. 1920 , 131 L.Ed.2d 985 (1995). “[A]ny doubts concerning the scope of arbitrable issues should be resolved in favor of arbitration.” Moses H. Cone Mem’l Hosp. v. Mercury Const. Corp., 460 U.S. 1, 24-25 , 103 S.Ct. 927 , 74 L.Ed.2d 765 (1983). Thus, arbitration should only be denied where “it may be said with positive assurance that the arbitration clause is not susceptible of an interpretation that covers the asserted dispute.” AT & T Tech., Inc. v. Commc’n Workers, 475 U.S. 643, 650 , 106 S.Ct. 1415 , 89 L.Ed.2d 648 (1986) (quoting United Steelworkers v. Warrior & Gulf Navigation Corp., 363 U.S. 574, 582-83 , 80 S.Ct. 1347 , 4 L.Ed.2d 1409 (I960)).

B. Motion to Dismiss

Under Fed.R.Civ.P. 12(b)(7), a party may bring a motion to dismiss for “failure to join a party under Rule 19.” Fed.R.Civ.P. 19 provides that a party “must be joined” if, in that party’s absence, the court “cannot accord complete relief among existing parties.” Fed. R.Civ.P. 19(a). Under Rule 19, courts undertake a three-step analysis to determine whether an absent party should be joined. See E.E.O.C. v. Peabody W. Coal Co., 400 F.3d 774, 779 (9th Cir.2005). First, the court must determine whether the absent party is “necessary.” See Takeda v. Northwestern Nat’l Life Ins. Co., 765 F.2d 815, 819 (9th Cir.1985). A party is “necessary” if, inter alia, “complete relief cannot be accorded among those already parties” in that party’s absence. Id. (citing Fed. *895 R.Civ.P. 19(a)). Second, if the absent party is a “necessary party under Rule 19(a),” the court must determine “whether it is feasible to order that the absentee be joined.” Peabody W. Coal Co., 400 F.3d at 779 . Third, “if joinder is not feasible,” the court must determine “whether the case can proceed without the absentee, or whether the absentee is an ‘indispensable party' such that the action must be dismissed.” Id.

IV. DISCUSSION

A. Motion to Compel Arbitration

Defendant moves to compel Plaintiffs to arbitrate their claims, on the grounds that: (1) the claims in this action are “identical” to the claims brought against Defendant in a previous case brought by Plaintiffs’ counsel; and (2) the Court granted Defendant’s motion to compel arbitration in the previous case, which means that arbitration is also appropriate in this case. 10 Plaintiffs respond that the Court should not compel them to arbitrate their claims, on the grounds that: (1) the “legal basis upon which the Court relied in the prior action to compel those plaintiffs to arbitrate their claims against [Defendant] no longer applies,” because the Ninth Circuit opinion upon which the Court relied “is no longer valid”; 11 and (2) even if the legal basis upon which the Court relied in the prior action does still apply, arbitration should not be compelled in this case, as neither of the tests required for arbitration to be compelled are applicable. 12 The Court considers each ground in turn.

1. Continuing Validity of Mundi

At issue is whether the Ninth Circuit opinion—i.e., Mundi—on which the Court relied in determining that a non-signatory defendant may compel arbitration against a signatory plaintiff is still valid.

“Circuit law ... binds all courts within a particular circuit, including the court of appeals itself.” Hart v. Massanari, 266 F.3d 1155, 1171 (9th Cir.2001). “Thus, the first panel to consider an issue sets the law not only for all the inferior courts in the circuit, but also future panels of the court of appeals.” Id. “Once a panel resolves an issue in a precedential opinion, the matter is deemed resolved, unless overruled by the court itself sitting en banc, or by the Supreme Court.” Id.

Here, as discussed above, the Court relied upon the Ninth Circuit’s opinion in Mundi v. Union Security Life Insurance Company in reaching its decision regarding the applicability of equitable estoppel in this context. However, Plaintiffs contend that the Ninth Circuit has “recently ... declared] that Mundi ... is no longer valid.” (Arbitration Opp’n at 2.) For this proposition, Plaintiffs rely upon an unpublished opinion issued by the Ninth Circuit on March 5, 2012, in which the Ninth Circuit stated that another dis *896 trict court had erred by following Mundi rather than a Supreme Court decision that was issued several months after Mundi 13 Upon review, however, the Court finds that Plaintiffs’ contention is misguided. First, it is clear as a matter of Ninth Circuit law that Mundi, which is a precedential opinion, may only be overruled by the Ninth Circuit itself sitting en banc or by the Supreme Court. Hart, 266 F.3d at 1171 . Thus, the Ninth Circuit’s unpublished opinion in Allianz cannot have “declared” Mundi invalid, as a matter of Ninth Circuit law. Id. Second, the Court finds that it is not clear that the Supreme Court’s opinion in Arthur Andersen “overruled” Mundi. In Arthur Andersen, the Supreme Court held that state law “is applicable to determine which contracts” are binding and enforceable, under the Federal Arbitration Act, “if that [state] law arose to govern issues concerning the validity, revocability, and enforceability of contracts generally.” Arthur Andersen, 556 U.S. at 630-31, 129 S.Ct. 1896 (emphasis in original). 14 Thus, Arthur Andersen does not state categorically that courts must always apply state law, rather than federal common law, in this type of situation. Rather, it states only that courts should apply state law if that law “arose to govern [certain] issues.” 15 Id.

Further, the Court observes that it is unclear that the Ninth Circuit, in *897 Mundi, was expounding “federal common law.” It is true that the FAA created a “federal common law of arbitrability which preempts state law disfavoring arbitration.” See, e.g., Circuit City Stores, Inc. v. Adams, 279 F.3d 889, 892 (9th Cir.2002) (citations omitted). Nonetheless, courts have long recognized that in “determining the validity of an agreement to arbitrate, federal courts should apply ordinary state-law principles that govern the formation of contracts.” Id. (citation and internal quotations omitted). Indeed, the court in Mundi expressly recognized this principle. 16 The court went on to explain that “[gjeneral contract and agency principles”—in particular, the principle of equitable estoppel—“apply in determining the enforcement of an arbitration agreement by or against nonsignatories.” Mundi, 555 F.3d at 1045-46. In the course of its elaboration of the principle of equitable estoppel in the arbitration context, the court in Mundi looked to the decisions of other circuit courts. See id. However, those other decisions were themselves grounded in “ordinary state-law principles,” rather than in a freestanding “federal common law” governing the validity of contracts. 17 Thus, the mere fact that the court in Mundi referred to other federal court opinions in formulating its holding regarding equitable estoppel does not mean that Mundi was stating “federal common law.”

In sum, the Court declines to adopt Plaintiffs’ interpretation of Allianz. In reaching this conclusion, the Court is mindful of the Ninth Circuit’s admonition that its non-precedential opinions are “not written in a way that will be fully intelligible to those unfamiliar to the case,” and in particular its admonition that the “rule of law [in non-precedential opinions] is not announced in a way that makes it suitable for governing future cases.” Hart, 266 F.3d at 1178 . As the Ninth Circuit explained in Hart , the advantage of issuing non-precedential opinions is that the appellate court may thereby conserve judicial time and effort, freeing it to “spend the requisite time drafting precedential opinions in [other] cases.” Id. The court went on to observe that, given the nature of nonprecedential opinions, it would be inefficient to allow parties to cite them, insofar as the absence of “precisely crafted holdings” in such opinions would tempt “zealous counsel ... to seize upon superficial similarities between their clients’ cases and unpublished dispositions.” Id. It is true that, following Hart , the Ninth Circuit revised its rule regarding citation of unpublished dispositions and allowed them to be cited to the courts of the Ninth Circuit in certain circumstances. See 9th Cir. R. 36- *898 3. However, the Court finds that the reasoning in Hart applies to this case, especially given the fact that the court in Allianz did not announce a “rule of law” regarding the relation of Arthur Andersen to Mundi that is “fully intelligible to those unfamiliar with [Allianz ].” Hart, 266 F.3d at 1178 . 18

Accordingly, the Court finds that the Ninth Circuit’s opinion in Mundi is still valid with regard to the issue of whether a non-signatory defendant may compel arbitration against a signatory plaintiff.

2. Whether Equitable Estoppel May Be Applied in This Case

At issue is whether Defendant satisfies the requirements to invoke the doctrine of equitable estoppel against Plaintiffs to compel arbitration.

A defendant that is a non-signatory to an agreement providing for arbitration may compel arbitration of claims by a plaintiff that is a signatory to such an agreement on the basis of equitable estoppel, so long as two requirements are met: (1) the subject matter of the dispute must be “intertwined with the contract providing for arbitration”; and (2) there must be a “relationship among the parties of a nature that justifies a conclusion that the party which agreed to arbitrate with another entity should be estopped from denying an obligation to arbitrate a similar dispute with the adversary which is not a party to the arbitration agreement.” In re Apple & AT & TM Antitrust Litig., 826 F.Supp.2d at 1177 (citing Mundi, 555 F.3d at 1045-46).

Upon review, the Court finds that Defendant does not satisfy both requirements to invoke the doctrine of equitable estoppel in this case. In particular, the Court finds that Defendant has not shown that the subject matter of this dispute is “intertwined with the contract providing for arbitration,” insofar as two of Plaintiffs’ three causes of action-namely, their causes of action involving an alleged aftermarket for applications for the iPhonemight pertain solely to Defendant’s solitary actions with regard to applications for its iPhones, and thus might not be judged to be “intertwined with” the service agreement issued by ATTM. 19

The Court rejects Defendant’s contention that the Court should order Plaintiffs to arbitrate their claims in this case because these claims are “the same” as the claims that were subjected to arbitration in the In re Apple & AT & TM Antitrust Litigation. (Motion to Compel at 2-3.) In the earlier case, Apple moved to compel arbitration of all of the plaintiffs’ claims, including claims relating to an alleged aftermarket for applications, on the grounds that: (1) the plaintiffs in that case had “sought to certify a single class ... to pursue both [their] voice and data aftermarket claims and [their] applications af *899 termarket claims”; and (2) the Court had granted plaintiffs’ motion for class certification and “certified a unified class, adopting plaintiffs’ proposed class definition, to pursue both sets of claims.” 20 In its order compelling arbitration, the Court specifically found that the plaintiffs’ claims in that case were “intertwined” with the contract at issue, insofar as: (1) “[the plaintiffs] themselves have contended throughout [that case] that their antitrust and related claims against [ATTM and Apple] arise from their respective ATTM service contracts”; and (2) the Court had “certified a single unified class,” at the plaintiffs’ request, comprising “[a]ll persons who purchased or acquired an iPhone in the United States and entered into a two-year agreement with [ATTM] for iPhone voice and data service [at] any time from June 29, 2007, to the present.” In re Apple & AT & TM Antitrust Litig., 826 F.Supp.2d at 1178 (citations omitted) (emphasis added). Here, by contrast, Plaintiffs have not contended that any of their claims arise from ATTM service contracts. 21 Moreover, the Court has not yet certified any class in this case. Thus, the Court finds that its decision to compel arbitration, under the doctrine of equitable estoppel, of the claims in the In re Apple & AT & TM Antitrust Litigation is not apposite to the present Motion.

Below, the Court finds that ATTM is a necessary party, at least as to any claims relating to voice and data services. Plaintiffs are given leave to file an amended complaint adding ATTM should they wish to continue to pursue those claims. Because the disposition of the Motion to Compel Arbitration might be affected by the claims and parties in the Amended Complaint, the Court DENIES without prejudice Defendant’s Motion to Compel Arbitration.

B. Motion to Dismiss

Defendant moves to dismiss the Complaint under Fed.R.Civ.P. 12(b)(7), on the grounds that: (1) the Complaint fails to name ATTM as a Defendant; but (2) ATTM is both a necessary and an indispensable party, pursuant to Fed.R.Civ.P. 19. (Motion to Dismiss at 5-13.) Plaintiffs respond that ATTM is neither a necessary nor an indispensable party, pursuant to Rule 19. 22 The Court considers in turn the issues of whether ATTM is a necessary party and whether, if ATTM is a necessary party, it is feasible for ATTM to be joined.

1. Is ATTM a Necessary Party?

At issue is whether ATTM is a necessary party, pursuant to Fed.R.Civ.P. 19(a).

As a general rule, it “is not necessary for all joint tortfeasors to be named as defendants in a single lawsuit.” Temple v. Synthes Corp., Ltd., 498 U.S. 5, 7 , 111 S.Ct. 315 , 112 L.Ed.2d 263 (1990). However, if a plaintiffs antitrust claims require a court to evaluate the conduct of an absent party that is alleged to be an antitrust co-conspirator with a defendant, thereby “substantially implicating [the] interests” of that party, the absent party is necessary pursuant to Rule 19(a). 23

Based on the allegations above, the Court finds that ATTM is a necessary party pursuant to Rule 19(a). In particular, the Court finds that in order to evaluate Plaintiffs’ antitrust claims in regard to the alleged conspiracy to monopolize the alleged iPhone Voice and Data Services Aftermarket, the Court will be required to evaluate ATTM’s conduct, insofar as Plaintiffs allege, inter alia, that ATTM unlawfully achieved market power in that Aftermarket due to the conspiracy and thereby foreclosed other companies from entering the market. (Complaint ¶ 98.) Such an evaluation of ATTM’s conduct would necessarily implicate the interests of ATTM, which means that ATTM is a necessary party pursuant to Rule 19(a). Laker Airways, 182 F.3d at 847-48.

Plaintiffs’ contention that the Court should not rely upon Laker Airways because it is an “outlier that has not been accepted in the Ninth Circuit” is misguided. (Dismiss Opp’n at 12-15.) First, Plaintiffs cite no case in which the Ninth Circuit has disapproved of the rule regarding antitrust co-conspirators enunciated in Laker Airways; nor is the Court aware of any such case. Second, the court in Laker Airways itself relied upon a decision from the Ninth Circuit in formulating its statement of that rule, 24 which belies Plaintiffs’ contention that the rule is not “accepted” in the Ninth Circuit. Finally, the Court observes that several other district courts within the Ninth Circuit have recently cited with approval the rule enunciated in Laker Airways. 25

*901 Accordingly, the Court finds that ATTM is a necessary party.

2. Is It Feasible for ATTM to Be Joined?

At issue is whether it is feasible for ATTM to be joined.

If an absent party is a necessary party under Rule 19(a), the court must determine whether it is “feasible” to order that the absent party be joined. Peabody W. Coal Co., 400 F.3d at 779 . There are three circumstances “in which joinder is not feasible”: (1) “when venue is improper”; (2) “when the absentee is not subject to personal jurisdiction”; and (3) “when joinder would destroy subject matter jurisdiction.” Id.

Here, the Court finds that it is feasible for ATTM to be joined, insofar as this is a proper venue, ATTM is subject to the Court’s personal jurisdiction, and joinder would not destroy the Court’s subject matter jurisdiction. 26 Peabody W. Coal Co., 400 F.3d at 779 .

Plaintiffs contend that joinder of ATTM is not feasible because: (1) ATTM “will immediately move to compel arbitration of the claims against it”; (2) the Court is “practically certain” to grant such a motion; and (3) in that case, ATTM would be “dismissed for improper venue.” (Dismiss Opp’n at 15.) However, the Court finds that each aspect of this contention is misguided. Plaintiffs cite no case for the proposition that courts should consider the possibility that an absent party will move to compel arbitration when conducting a feasibility analysis under Rule 19; nor is the Court aware of any case standing for that proposition. Plaintiffs’ other contentions are premature and speculative.

Accordingly, the Court finds that it is feasible for ATTM to be joined.

In sum, because the alleged conspiracy is with ATTM to monopolize or attempt to monopolize the aftermarket for voice and data services, the Court finds that ATTM is a necessary party which can, and therefore must, be joined. Therefore, the Court GRANTS Defendant’s Motion to Dismiss for failure to join a necessary party under Fed.R.Civ.P. 12(b)(7). 27

V. CONCLUSION

The Court DENIES without prejudice Defendant’s Motion to Compel Arbitration and GRANTS in part Defendant’s Motion to Dismiss. The Court finds that ATTM is a necessary party and therefore must be joined as a party under Fed.R.Civ.P. 12(b)(7). All other grounds for dismissal are DENIED as premature. 28

*902 The Court ORDERS that ATTM be made a party to this action. 29 On or before July 31, 2012, Plaintiffs shall file an Amended Complaint consistent with the terms of this Order.

The Court previously vacated the Case Management Conference in this case in light of the pending Motions. The Court now sets September 24, 2012 at 10 a.m. as the new Conference date. On or before September 14, 2012, the parties shall file a Joint Case Management Statement with a proposed schedule on how this case should proceed.

. Named Plaintiffs are Robert Pepper, Stephen H. Schwartz, Edward W. Hayter, Harry Bass, Eric Terrell, James Blackwell and Crystal Boykin.

. (Defendant Apple's Notice of Motion and Motion to Compel Arbitration of Claims; Memorandum of Points and Authorities in Support Thereof, hereafter, "Motion to Compel,'' Docket Item No. 48.)

. (Defendant Apple’s Notice of Motion and Motion to Dismiss Plaintiffs' Consolidated Complaint; Memorandum of Points and Authorities in Support Thereof, hereafter, "Motion to Dismiss,” Docket Item No. 37 (filed under seal).)

. (hereafter, "Complaint,” Docket Item No. 26.)

. A SIM card is a removable card that allows phones to be activated, interchanged, swapped out and upgraded. (Complaint ¶ 40.) The SIM card is tied to the phone's network, rather than to the physical phone device itself. (Id.) Thus, to switch from, e.g., the ATTM phone network to the T-Mobile phone network, the owner of a cell phone may remove from his phone the SIM card associated with the ATTM network and replace it with a SIM card associated with the T-Mobile network. (Id. ¶ 41.) However, certain SIM cards are "locked” to particular phones, which means that the owner of that phone cannot change networks simply by changing SIM cards. (Id. ¶ 44.) In the case of such locked SIM cards, the network can only be changed if the owner of the phone is provided with an “unlock code” which unlocks the SIM card. (Id.)

. (See Docket Item No, 1 in Terrell v. Apple Inc., No. C 12-00259 JW.)

. (See Order Vacating Case Management Conference; Consolidating Cases; Denying Motion to Dismiss as Moot, Docket Item No. 25.)

. (Order Granting in Part Motion to Change Time, Docket Item No. 31.)

. (See Order Appointing Interim Class Counsel at 3, Docket Item No. 34.)

. (Motion to Compel at 1-2.) The previous case is In re Apple & AT & TM Antitrust Litigation. On December 1, 2011, the Court granted motions to compel arbitration that had been brought by the defendants in that case, namely, Apple and ATTM. See In re Apple & AT & TM Antitrust Litig., 826 F.Supp.2d 1168, 1171 (N.D.Cal.2011).

. In the previous case, the Court relied upon the Ninth Circuit’s opinion in Mundi v. Union Security Life Insurance Company to reach the conclusion that the defendant, Apple, could invoke the doctrine of equitable estoppel to compel arbitration against plaintiffs, even though Apple was a non-signatory to the arbitration agreement at issue in the case. See In re Apple & AT & TM Antitrust, 826 F.Supp.2d at 1175-79 (discussing Mundi v. Union Sec. Life Ins. Co., 555 F.3d 1042 (9th Cir.2009)).

. (Plaintiffs’ Opposition to Defendant Apple Inc.’s Motion to Compel Arbitration at 3-17, hereafter, "Arbitration Opp’n,” Docket Item No. 61.)

. See Allianz Global Risk U.S. Ins. Co. v. Gen. Elec. Co., No. 10-55451, 2012 WL 689957 , at *1 (9th Cir. Mar. 5, 2012) (citing Mundi and Arthur Andersen v. Carlisle, 556 U.S. 624 , 129 S.Ct. 1896 , 173 L.Ed.2d 832 (2009)). Only two sentences of the Ninth Circuit’s unpublished opinion in Allianz speak to this issue; they are as follows: "The district court held that [the defendant] was equitably estopped from refusing to arbitrate under its own contractual arbitration clause, where the issues in [the plaintiff’s] claim are intertwined with issues arising out of the manner in which [the defendant] performed its obligations under [a sales contract]. The district court applied our court’s decision in [Mundi ], while under the Supreme Court’s decision in [Arthur Andersen ], the district court should have applied state law, not federal common law.” Id. Because the court in Allianz found that this "misstatement of the applicable law [was] not material,” it did not elaborate this discussion any further. Id.

. Two years after Arthur Andersen , the Supreme Court held that a state-law rule that "interferes with arbitration” was preempted by the Federal Arbitration Act ("FAA”), insofar as that rule was an "obstacle to the accomplishment of the FAA’s objectives.” AT & T Mobility LLC v. Concepcion, -U.S. -, 131 S.Ct. 1740 , 1748-50, 179 L.Ed.2d 742 (2011). In Concepcion, the Supreme Court did not discuss its prior decision in Arthur Andersen in any way, leaving the relationship between those two decisions unclear. In the aftermath of Concepcion, some courts have reconciled the two decisions by explaining that the "interpretation of an arbitration agreement is ... generally a matter of state law, unless application of state-law rules would stand as an obstacle to the accomplishment of the FAA’s objectives.” See, e.g., Yahoo! Inc. v. Iversen, 836 F.Supp.2d 1007, 1009-10 (N.D.Cal.2011) (internal quotations and citations omitted) (emphasis added).

. As another district court in the Ninth Circuit has recently explained, it is unclear whether Arthur Andersen "effected an Erie-like abrogation of federal law in favor of state law” or merely "affirm[ed] the federal nature of the estoppel question, but only to the extent that the federal law tracks traditional principles of state law.” Kingsley Capital Mgmt., LLC v. Sly, 820 F.Supp.2d 1011, 1021-23 (D.Ariz.2011) (internal quotations omitted) (collecting cases). At least one circuit has declined to clarify, post-Arthur Andersen, whether the "principles of contract and agency law” that "may be called upon to bind a nonsignatory” to an arbitration agreement are to be drawn from state law or from the “federal substantive law of arbitrability.” DK Joint Venture 1 v. Weyand, 649 F.3d 310, 314 (5th Cir.2011) (citations omitted). In DK Joint Venture, the Fifth Circuit refused to decide whether state or federal law applies in this situation, on the basis of the court's determination that "both bodies of law lead [in a case involving Texas law] to the same conclusion.” Id.

. See Mundi, 555 F.3d at 1044 (stating that "[w]hen deciding whether the parties agreed to arbitrate a certain matter,” courts “generally ... should apply ordinary state-law principles that govern the formation of contracts") (citation omitted).

. As an example, the court in Mundi observed that one of the two “types of equitable estoppel in the arbitration context” that had previously been examined by the Ninth Circuit was one in which a nonsignatory may be held to an arbitration clause where it "knowingly exploits the agreement containing the arbitration clause despite never having signed the agreement.” Mundi, 555 F.3d at 1046 (internal quotations and citations omitted). For this proposition, the court in Mundi relied upon the Ninth Circuit's earlier opinion in Comer v. Micor, Inc. See id. (citing Comer v. Micor, Inc., 436 F.3d 1098 (9th Cir.2006)). In Comer itself, however, the Ninth Circuit recognized that in considering the question of “whether a particular party is bound by [an] arbitration agreement,” the “liberal federal policy regarding the scope of arbitrable issues is inapposite.” Comer, 436 F.3d at 1104 n. 11 (emphasis in original) (citation omitted). Instead, the court in Comer stated that "Mrdinary contract principles determine who is bound,” and expressly relied upon “ordinary contract and agency principles” in arriving at its holding. Id. at 1101-04 & n. 11 (citations omitted).

. Moreover, the Court observes that on February 1, 2012, it certified for interlocutory appeal the issue of whether a non-signatory defendant may assert equitable estoppel against a signatory plaintiff, as that issue was presented by the Court's order in the In re Apple & AT & TM Antitrust Litigation that relied upon Mundi. See In re Apple & AT & TM Antitrust Litig., No. C 07-05152 JW, 2012 WL 293703 (N.D.Cal. Feb. 1, 2012). However, on April 27, 2012—i.e., after the Ninth Circuit issued its unpublished order in Al lianz—the Ninth Circuit denied the plaintiffs in that case permission to appeal that issue.

See In re Apple iPhone 3G Prods. Liability Litig., MDL No. C 09-02045 JW, 859 F.Supp.2d 1084 , 1095 n. 38, 2012 WL 1622643 , at *8 n. 38 (N.D.Cal. May 9, 2012) (discussing the Ninth Circuit’s denial).

. The contract at issue is ATTM's Wireless Service Agreement (“WSA”), which is not mentioned in Plaintiffs' Complaint in this case. The Court discussed the WSA in its orders in the In re Apple & AT & TM Antitrust Litigation. See, e.g., In re Apple & AT & TM Antitrust Litig., 2012 WL 293703 , at *2.

. (See Defendant Apple’s Notice of Motion and Motion to Compel Arbitration and for Decertification at 14-15, Docket Item No. 514 in No. C 07-05152 JW (emphases added).)

. In fact, Plaintiffs expressly contend that their claims do not rely “upon the WSA in any way.’’ (Arbitration Opp’n at 12.) At this time, the Court does not reach the question of whether Plaintiffs must rely upon the WSA to advance any or all of their claims.

. (Plaintiffs’ Opposition to Defendant Apple Inc.'s Motion to Dismiss Consolidated Complaint, hereafter, “Dismiss Opp’n” (filed under seal).)

. See Laker Airways, Inc. v. British Airways, PLC, 182 F.3d 843, 847-48 (11th Cir.1999) *900 (citing Occidental Petroleum Corp. v. Buttes Gas & Oil Co., 331 F.Supp. 92, 105-06 (C.D.Cal.1971), affirmed, 461 F.2d 1261 (9th Cir.1972)).

. The court in Laker Airways relied upon a decision of the Central District of California. See Laker Airways, 182 F.3d at 847 (citing Occidental Petroleum, 331 F.Supp. at 105-06 ). In Occidental Petroleum, the district court explained that while it is "generally” true that joint tortfeasors need not be joined, that principle "must be applied in context.” 331 F.Supp. at 105-06 . In particular, the court found that an absent party’s "status as a joint tortfeasor” did not "negate its status as a contractual party[] with interests that are covered by Rule 19(a).” Id. at 106 . The district court's decision was affirmed by the Ninth Circuit in a per curiam opinion that simply stated that the district court’s "extensive and well-researched opinion” was “correct.” Occidental Petroleum Corp. v. Buttes Gas & Oil Co., 461 F.2d 1261 , 1261 (9th Cir.1972).

. See Dollens v. Target Corp., No. C 11-03265 RMW, 2011 WL 6033014 , at *2 (N.D.Cal. Dec. 5, 2011) (citing to Laker Airways to support the court's conclusion that an absent party should be joined as a defendant, insofar as the court's analysis of another party's liability would "necessarily require the court to evaluate the [absent party’s] conduct in a manner that would surely implicate her interests”); In re Toyota Motor Corp., 785 F.Supp.2d 883, 906 (C.D.Cal.2011) (citing to Laker Airways for the proposition that an absent joint tortfeasor is a necessary party if it is an "active participant in the allegations that *901 are critical to the disposition of the litigation”).

. In a recent case, the Court similarly found that it was feasible, under Rule 19, for ATTM to be joined as a defendant. See In re Apple iPhone 3G Prods. Liability Litig., MDL No. C 09-02045 JW, 2011 WL 6019217 , at *4 (N.D.Cal. Dec. 1, 2011).

. In its Motion to Dismiss, Defendant also moves, under Fed.R.Civ.P. 12(b)(6), to dismiss Plaintiffs’ Third Cause of Action—namely, their cause of action for conspiracy to monopolize the iPhone Voice and Data Services Aftermarket—for failure to state a claim. (Motion to Dismiss at 17-22.) However, Defendant’s contentions as to this issue are predicated on their contention that such a claim cannot be stated in the absence of ATTM. (See id. at 17 (contending that "[wjithout ATTM in the picture, Plaintiffs cannot adequately allege a conspiracy to make ATTM a monopolist”).) In light of the Court’s ruling that ATTM must be made a party, the Court DENIES as premature Defendant’s Motion to Dismiss Plaintiffs' Third Cause of Action, without prejudice to renew on a different ground after ATTM has been joined.

. Accordingly, the Court DENIES as moot Plaintiffs’ Civil L.R. 7-3 Motion for Permission to File a Sur-Reply Brief on Apple Inc.’s Motion to Compel Arbitration, Docket Item No. 66. In addition, Defendant has objected to certain evidence submitted by Plaintiffs in *902 relation to the Motion to Compel Arbitration. See Defendant Apple's Objection to Evidence Submitted by Plaintiffs in Connection with Apple’s Motion to Compel Arbitration, Docket Item No. 69. However, the Court has not relied upon any of the evidence at issue. Accordingly, the Court OVERRULES as moot Defendant’s objections. Finally, after the June 18 hearing, Plaintiffs filed a Motion for Leave to File a Supplemental Brief addressing certain issues. (See Plaintiffs' L.R. 7-3 Motion for Permission to File a Supplemental Brief on Apple Inc.’s Motion to Dismiss [ECF No. 37] and Motion to Compel Arbitration [ECF No. 48], hereafter, "Supplemental Brief Motion,” Docket Item No. 72.) However, upon review, the Court finds that the Supplemental Brief provided in this Motion is either unnecessary, insofar as it merely reiterates arguments regarding Rule 19 that have already been made in the parties' briefing, or moot, insofar as it opposes the Motion to Compel Arbitration. (See id.) Accordingly, the Court DENIES the Supplemental Brief Motion.

. This Order is not intended to require that Plaintiffs maintain claims based on an alleged voice and data services aftermarket. Instead, it holds that insofar as Plaintiffs wish to maintain such claims, ATTM must be added as a party.