The plaintiffs, an assortment of environmental activist groups, petitioned the Environmental Protection Agency (EPA) to "use its power" to control nitrogen and phosphorous pollution" in the Mississippi River Basis and the Northern Gulf Of Mexico. The EPA chose not to do so, noting that federal rulemaking was not the most effective or practical means of addressing such concerns and that the EPA's policy (consistent with the Clean Water Act (CWA)) was to allow the states to develop and adopt their own standards. The plaintiffs sued, claiming that the EPA had violated the Administrative Procedure Act and the CWA by declining to make a "necessity determination." The EPA moved to dismiss the case on the basis that the agency had the discretion to decline to make a necessity determination that wasn't reviewable by the court. The trial court ruled that it had jurisdiction to review the EPA's decision and ordered the EPA to make a necessity determination. On further review, the appellate court vacated the trial court's decision. The appellate court determined that the courts have jurisdiction to review a denial of a rulemaking petition. The court also determined that the EPA had discretion to decide not to make a necessity determination due to the broad language in 33 U.S.C. Sec. 1313(c)(4)(B). The court remanded the case to the trial court to decide in the first instance whether the EPA's explanation for why it declined to make a necessity determination was legally sufficient. The court also informed the trial court that in doing so the court was to give great deference to the EPA and use a rational basis review standard. Gulf Restoration Network, et al. v. McCarthy, No. 13-31214, 2015 U.S. App. LEXIS 5602 (5th Cir. Apr. 7, 2015).