6th Cir.

Michigan Department of Environment, Great Lakes, and Energy v. Gerald R. Ford International Airport Authority

June 30, 2026 ·24-1734 ·Published ·Siler · By Aisha Johnson

The Sixth Circuit affirmed a district court order severing state environmental claims from federal third-party claims and remanding the state claims to state court. The court held that the district court did not abuse its discretion in declining supplemental jurisdiction and that the Airport Authority was barred from relitigating its federal-officer removal argument under the law of the case doctrine.

Background

The State of Michigan sued the Gerald R. Ford International Airport Authority in state court over alleged PFAS contamination from aqueous film-forming foam. The Airport Authority removed the case to federal court under the federal-officer removal statute, but the district court remanded it, a decision the Sixth Circuit affirmed. After remand, the Airport Authority filed third-party claims against AFFF manufacturers, who also removed the case to federal court. The district court then severed the State’s claims from the third-party claims and remanded the State’s claims back to state court, declining supplemental jurisdiction over them.

The court’s reasoning

The Sixth Circuit reviewed the severance ruling for abuse of discretion, finding that while the claims shared some factual overlap, the legal issues and required proof were distinct enough to favor severance for judicial economy. Regarding supplemental jurisdiction, the court held that the district court acted within its discretion to decline jurisdiction because the state-law claims substantially predominated and exceptional circumstances existed, including the case’s history of being remanded once before. Finally, the court applied the law of the case doctrine to bar the Airport Authority from relitigating its federal-officer removal argument, as the relationship between the Airport Authority and the FAA had not changed since the prior appeal.

What it means going forward

State environmental enforcement claims regarding PFAS contamination at the airport will proceed in Michigan state court, while third-party claims against manufacturers will continue in federal multidistrict litigation.