Last week, in Williamson v. Mazda Motor of America, Inc., the Supreme Court of the United States reversed a California decision and made product liability actions involving the failure to install inner-seat lap/shoulder-combination seatbelts available once again in state courts. In a unanimous decision, the Court held that implied preemption did not apply, and distinguished the case from Geier v. American Honda Motor Co. (2000).

In Geier, state law stood as an obstacle to the accomplishment of a significant federal regulatory objective: giving manufacturers a choice among different kinds of passive restraint systems. The Department of Transportation (DOT) had long thought it important to leave manufacturers with a choice of systems, and federal regulations, designed to protect that industry choice, preempted conflicting state law.

However, the Court in Williamson found that while the California tort suit would similarly restrict industry choice by alleging a manufacturer should have installed a particular restraint system, the choice in this case was not a significant regulatory objective. DOT rejected a regulation requiring lap/shoulder-combination seatbelts in rear seats in 1984 due to consumer acceptance concerns. But by 1989, changed circumstances led DOT to require manufacturers to install such seatbelts for rear outer seats but to retain a manufacturer choice for rear inner seats. DOT thought that the same requirement for inner seats would not be cost effective, a much different regulatory analysis than seeking to spur development of alternative safety devices in Geier. Cost-effectiveness alone cannot show that DOT sought to forbid common-law tort suits and, therefore, preemption does not apply to such cases.