On November 16, 2016, in Mason v. Lockwood, Andrews & Newnam, P.C., the US Court of Appeals for the Sixth Circuit held that each putative class member's residence was presumptively his domicile for purposes of the Class Action Fairness Act's (CAFA) local controversy exception. In so holding, the court created a circuit split between other circuit courts that have considered the issue ( (6th Cir. Nov. 16, 2016)).

This case arose out of the Flint, Michigan water crisis. The City of Flint hired the defendants to rehabilitate Flint's water treatment facility and control the quality of drinking water drawn from the Flint River. After the water became tainted with lead, Flint residents suffered severe health consequences. A group of Flint residents sued the defendants for professional negligence and sought relief on behalf of themselves as well as other residents and property owners in Flint who drew water from the Flint River.

The defendants removed the action to federal court and the plaintiffs moved to remand the case under the local controversy exception to the Class Action Fairness Act of 2005 (CAFA). Under CAFA's local controversy exception, if the moving party meets three factors, including that more than two-thirds of the proposed class members are citizens of the state where the action originally was filed, a federal district court must decline jurisdiction (28 U.S.C. § 1332(d)(4)(A)(i)(I)). Therefore, a party invoking the local controversy exception must establish the domicile of the proposed class members.

The defendants argued that the plaintiffs' allegations of residency were not sufficient to establish citizenship of the putative class for purposes of the exception. The district court disagreed and granted the plaintiffs' motion to remand, finding that more than two-thirds of the class members likely were Michigan citizens. The defendants appealed.

The Sixth Circuit affirmed the district court's opinion, finding that the plaintiffs successfully established the class citizenship requirement for CAFA's local controversy exception. The court found that the plaintiffs were entitled to the rebuttable presumption that a person's residence is his domicile. The court noted other attributes of the putative class members' residency that bolstered the presumption that they are domiciles, including their length of residence, property ownership, and the proximity of Flint to Michigan's state line.

In applying the residency-domicile presumption to the context of CAFA's local controversy exception, the Sixth Circuit split from five other circuits that have considered the issue, including the Fifth, Seventh, and Tenth Circuits.