Here is the opinion in Unkechaug Indian Nation v. Treadwell.
When acting within its territorial boundaries and with respect to internal matters, an Indian Nation retains the sovereignty it enjoyed prior to the adoption of the United States Constitution except to the extent that its sovereignty has been abrogated or curtailed by Congress (see Montana v United States, 450 US 544, 564; United States v Kagama, 118 US 375, 381-382; Cayuga Nation v Campbell, 34 NY3d 282, 291, 293). As such, “tribes possess the common-law immunity traditionally enjoyed by sovereign powers” (Oneida Indian Nation v Phillips, 981 F3d 157, 170 [2d Cir]). As the Supreme Court correctly determined in the May 1, 2019 order, in seeking a declaration with respect to Curtis’s right to occupy the disputed portion of the subject property, the Nation waived its sovereign immunity as to that issue (see Rupp v Omaha Indian Tribe, 45 F3d 1241, 1244 [8th Cir] ; Cayuga Indian Nation of New York v Seneca County, New York, 260 F Supp 3d 290, 299 [WD NY]). However, “a waiver of sovereign immunity cannot, on its own, extend a court’s subject matter jurisdiction” (Oneida Indian Nation v Phillips, 981 F3d at 171), and “[w]aivers of [sovereignty] are to be strictly construed in favor of the Tribe” (Wells Fargo Bank, N.A. v Chukchansi Economic Dev. Auth., 118 AD3d 550, 551 [internal quotation marks omitted]; see Sue/Perior Concrete & Paving, Inc. v Seneca Gaming Corp., 99 AD3d 1203, 1204).
Because of the retained sovereignty of Indian Nations, the subject matter jurisdiction of state courts “must be predicated on explicit authorization from Congress to address matters of tribal self-government” (Cayuga Nation v Campbell, 34 NY3d at 292). Moreover, the courts of this State have rejected the “paternalistic view” that Indian Nations within its borders are “disadvantaged” by their “inability to rely on New York courts” to determine internal disputes, since “the use of dispute resolution mechanisms other than courts is itself an exercise of the right to self-govern in a manner consistent with tribal traditions and oral law” (id. at 296; see Cayuga Nation v Tanner, 824 F3d 321, 327 [2d Cir]). Thus, “‘when it comes to Indian affairs, state courts are courts of limited jurisdiction'” (Cayuga Nation v Campbell, 34 NY3d at 296, quoting Bowen v Doyle, 880 FSupp 99, 114 [WD NY], affd 230 F3d 525 [2d Cir]).