SC20599 - Gershon v. Back (Dissolution of Marriage; Choice of Law; Whether New York Law is Substantive Rather Than Procedural for Choice-of-Law Purposes When Law Would Require Litigant Seeking Postjudgment Relief in Marital Dissolution Case to File Plenary Action Rather Than Motion to Open Dissolution Judgment; "New York's so-called "plenary action rule" requires a party seeking to modify or vacate a separation agreement that survives a final judgment of divorce to file a plenary action on the contract instead of a motion to open, modify or vacate the divorce judgment. This certified appeal requires us to determine whether New York's plenary action rule is procedural or substantive for choice of law purposes. The trial court concluded that the rule was substantive and dismissed for lack of subject matter jurisdiction the motion, filed by the plaintiff, Elana Gerson, to open and set aside the final judgment of divorce. The Appellate Court agreed that the New York rule was substantive but disagreed that the trial court lacked subject matter jurisdiction and, therefore, concluded that the plaintiff's motion should have been denied instead of dismissed. Gershon v. Back, 201 Conn. App. 225, 253–54, 242 A.3d 481 (2020). We affirm the judgment of the Appellate Court.")