The court relied on the fact that trailers have no motor and are not “self-propelled.” As a result, the court concluded that trailers are not “motor vehicles” and are not within the scope of EPA’s or NHTSA’s regulatory authority. The dissenting judge agreed with the majority that EPA cannot regulate trailers directly, under its existing statutory authority, but noted that EPA could instead regulate tractors “including the types of trailers they are allowed to pull” and could regulate the assembler of the tractor-trailer to ensure the assembled tractor-trailers meet emission standards. However, the dissenting judge disagreed that NHTSA exceeded its authority by issuing fuel efficiency standards for trailers. Unlike the Clean Air Act, NHTSA’s enabling laws do not define the term “vehicle,” and the judge determined that NHTSA reasonably applied a long-established definition that includes commercial trailers.
This decision regarding the scope of EPA’s and NHTSA’s regulatory authority over “motor vehicles” will certainly inform the agencies’ approach to future mobile source GHG rules, as well as future court decisions on EPA’s authority to set and enforce GHG emission standards under the Clean Air Act.
Authored by Joanne Rotondi, Katie Lannon, Hannah Graae, and Hannah Roskey.