From Mt Holly Citizens in Action, Inc. v. Township of Mount Holly, 2009 U.S. Dist. LEXIS 100032 (D.N.J. Oct. 23, 2009):

Plaintiffs claim that the Township's use of its municipal powers to redevelop existing low income residential neighborhoods violates the General Welfare Clause of the New Jersey Constitution. Plaintiffs' claim is based on the Mt. Laurel doctrine, which prohibits municipalities from using their zoning laws to exclude lower income households and obligates them to affirmatively provide a realistic opportunity for construction of its fair share of law and moderate income housing.... The Mt. Laurel doctrine, however, has never been applied to municipal redevelopment powers. The Township argues, and plaintiffs agree, that because this claim is one of first impression under New Jersey state law, this Court should decline subject matter jurisdiction over this state law claim pursuant to 28 U.S.C. § 1367(c)(1), and dismiss this claim without prejudice. The Court agrees with this approach. See Trump Hotels & Casino Resorts, Inc. v. Mirage Resorts Inc., 140 F.3d 478, 487 (3d Cir. 1998) (citing 28 U.S.C. § 1367(c)(1); Borough of West Mifflin v. Lancaster, 45 F.3d 780, 788 (3d Cir. 1995)) (stating that supplemental jurisdiction is exercised as a matter of discretion, and a court may decline to exercise supplemental jurisdiction over a state law claim where "the claim raises a novel or complex issue of state law"). This is especially true when a claim turns on a interpretation of a state constitution. Kadetsky v. Egg Harbor Tp. Bd. Of Ed., 164 F. Supp. 2d 425, 436 (D.N.J. 2001). Here the need for deference is even more pronounced. The Mt. Laurel doctrine, its judicial reiteration, the legislative response, the continuing implementation of an administrative process, and the intensely local impact of this evolving right, present a complex web best left to the expertise and sound judgment of the New Jersey courts.