Washington-St. Tammany Elec. Coop., Inc. v. La. Generating, LLC, 2020 U.S. Dist. LEXIS 27177 (M.D. La. Feb. 20, 2020):

¹ At oral argument, the Court also heard argument on Louisiana Generating LLC's Motion to Disqualify Counsel for Plaintiffs. (Doc. 203.) The Court is ruling on the Motion to Dismiss rather than the Motion to Disqualify because, as the Supreme Court has explained, subject-matter jurisdiction is "fundamentally primary." Leroy v. Great W. United Corp., 443 U.S. 173, 180, 99 S. Ct. 2710, 61 L. Ed. 2d 464 (1979). In addition, there is Fifth Circuit dicta that supports the proposition that where a court does not have subject matter jurisdiction, a motion to disqualify counsel is moot. Enable Mississippi River Transmission, LLC v. Nadel & Gussman, LLC, 844 F.3d 495, 501 (5th Cir. 2016) ("Having concluded that this court lacks subject matter jurisdiction to hear the underlying suit, we deny as moot Enable's motion to disqualify Nadel's counsel.") In addition, as a general rule a jurisdictional question is decided first, as the Southern District Mississippi [Heimer v. Knight, No. 3:13CV115TSL-JMR, 2013 U.S. Dist. LEXIS 202347, 2013 WL 12209912, at *1 (S.D. Miss. May 16, 2013)] stated,

Courts have regularly found that when faced with contemporaneous motions to dismiss for lack of jurisdiction and to disqualify an attorney, it is proper to decide the jurisdictional question first. See Rice v. Rice Found., 610 F.2d 471, 478 (7th Cir. 1979) (explaining that district court must have and exercise subject matter jurisdiction before ruling on motion to disqualify); [*3]  ESN, LLC v. Cisco Sys., Inc., 685 F. Supp. 2d 631, 645-646 (E.D. Tex. 2009) (concluding that subject matter jurisdiction was lacking so that case could not proceed on the merits, thus making motion to disqualify counsel moot); Dinger v. Gulino, 661 F. Supp. 438, 442 (E.D.N.Y. 1987) (concluding that question of jurisdiction should be considered before motion to disqualify attorney since "[a]bsent jurisdiction, it would be inappropriate for this Court to enter orders, even regarding a motion to disqualify an attorney"); Vetter v. Sands, No. 81 Civ. 5072, 1984 U.S. Dist. LEXIS 24145, 1984 WL 794, 2 (S.D.N.Y. Aug. 23, 1984) (finding that defense motion to disqualify plaintiffs' counsel should be continued until determination of motion to dismiss challenging subject matter jurisdiction); see also Arora v. Hartford Life and Annuity Ins. Co., 519 F. Supp. 2d 1021, 1024 (N.D. Cal. 2007) (granting motion to remand based on lack of subject matter jurisdiction and declining to rule on motion to disqualify). [Quoting Heimer v. Knight, No. 3:13CV115TSL-JMR, 2013 U.S. Dist. LEXIS 202347, 2013 WL 12209912, at *1 (S.D. Miss. May 16, 2013).]