The US Court of Appeals for the Tenth Circuit on Monday ordered the Environmental Protection Agency (EPA) to review the biofuel waivers it granted to three oil refineries.

The waivers exempt small oil refineries from complying with an amendment to the Clean Air Act passed by Congress in the early 2000s. The amendments require crude oil refineries to produce biofuels in addition to refined oil. In order to receive an exemption, a report from the Department of Energy needed to show that compliance would cause disproportionate economic hardship to the refinery. The statute limited the initial exemptions to 2011, but permitted extensions if necessary.

The court held that the EPA erred in approving the refineries petitions to extend their exemption waivers. While the refineries had received waivers, which had been extended prior to 2010, the EPA denied their petitions for further extensions. According to the court, the prior denials prevented the EPA from granting extensions later.

The court further held that the wording of the statute only permitted the EPA to extend exemptions granted before 2010. It is uncertain whether the refineries or EPA will appeal the decision to the Supreme Court.