JOHN K. BUSH, Circuit Judge. Plaintiffs Republic Building Company, Inc. and Michael Torres sought to develop condominiums at a property acquired from University Builders, Inc. But there was one problem: they needed rezoning approval from the Charter Township of Clinton, Michigan (the Township). After a protracted dispute over rezoning, plaintiffs sued the Township in Michigan state court to gain approval. The state court entered a consent judgment that dictated the conditions for rezoning the property and completing the project. Years later, after experiencing several setbacks, plaintiffs sought to amend the consent judgment, but the Township refused. Plaintiffs then filed this suit in federal district court, alleging several constitutional violations as well as a breach-of-contract claim. The Township moved to dismiss for lack of subject-matter jurisdiction, which the district court granted, finding plaintiffs’ complaint to be a collateral attack on the consent judgment. Contrary to the district court’s opinion, it did not lack subject-matter jurisdiction, but dismissal was nevertheless proper for failure to state a claim based on res judicata. We therefore AFFIRM.