On September 18, 2014, a divided panel of the U.S. Court of Appeals for the Fifth Circuit decided another Deepwater Horizon case. The case is United States v. Transocean Deepwater Drilling, Inc., and involves the statutory authority of the U.S. Chemical Safety and Hazard Investigation Board (CSB) to issue administrative subpoenas to Transocean, the operator of the Deepwater Horizon drilling unit, following the disaster on the Deepwater Horizon drilling unit in the Gulf of Mexico.

Transocean argued that the CSB lacked any authority to issue these subpoenas. According to Transocean, this was a "marine oil spill" from a vessel over which the CSB has no jurisdiction under the Clean Air Act (CAA). The lower court held that the CSB was only investigating the release of airborne gases following this explosion and spill on the Outer Continental Shelf (OCS) in the Gulf of Mexico, and since the Deepwater Horizon was not in fact a "vessel", the incident was not transportation-related and therefore the National Transportation Safety Board (NTSB) had no jurisdiction over the incident. By law, the CSB cannot investigate a "transportation-related" incident, but if the NTSB has no jurisdiction, then the CSB can step in.

The Fifth Circuit agreed, holding that while the drilling unit was a "vessel" for most purposes, it could also be considered to be a "stationary source" as that term is defined in the CAA because the Deepwater Horizon was physically attached to the seabed. Moreover, parsing the law, the Fifth Circuit held that there must be a category of marine oil spills that are not transportation-related and over which the NTSB lacks jurisdiction.

Judge Jones filed a strong dissent, remarking that virtually every Fifth Circuit decision to date has referred to the drilling unit as a "vessel", and to call it a stationary source because it was attached to the seabed is to ignore the fact that it was constantly in motion. Judge Jones also disagreed with the majority's ruling that the NTSB lacked authority to investigate this incident because it was not "transportation-related". Finally, Judge Jones remarked that, as a result of this ruling, "nearly all non-standard offshore vessels involved in oil and gas production on the OCS will become subject to CAA regulation and reports, in addition to all of the regulatory requirements of 'traditional vessels' imposed by the Coast Guard.