From U.S. ex rel Colucci v. Beth Israel Med. Ctr., 2009 U.S. Dist. LEXIS 117587 (S.D.N.Y. Dec. 15, 2009):

Courts have found substantial ground for difference of opinion where there is conflicting authority on the issue or the issue is particularly difficult and one of first impression in the Second Circuit. Klinqhoffer, 921 F.2d at 25. Disagreement among courts outside the circuit, however, does not alone support the certification of an interlocutory appeal. Ryan, Beck & Co., LLC v. Fakih, 275 F. Supp. 2d 393, 398 (E.D.N.Y. 2003). When cases cited by the moving party are "inapposite to the issue implicated by the instant action, of no persuasive authority, or both, no substantial ground for difference of opinion exists." . . .

The "mere presence of a disputed issue that is a question of first impression, standing alone, is insufficient to demonstrate substantial ground for difference of opinion." In re Flor, 79 F.3d 281, 284 (2d Cir. 1996). In the interest of judicial efficiency, and in light of the policy considerations underlying the final judgment rule, judges should exercise discretion in certifying an interlocutory appeal. "It is the duty of the district judge [faced with a motion for certification] to analyze the strength of the arguments in opposition to the challenged ruling when deciding whether the issue for appeal is truly one on which there is a substantial ground for dispute. Id. (emphasis in original) (citing Max Daetwyler Corp. v. Meyer, 575 F. Supp. 280, 283 (E.D.Pa. 1983)).