The D.C. Circuit denied petitions to review EPA's promulgation of a rule that regulates the emission of greenhouse gases from aircraft engines under CAA §231 by aligning domestic standards with those recently promulgated by the International Civil Aviation Organization (ICAO). Twelve states, the Di...

The D.C. Circuit granted in part and denied in part petitions to review EPA's revisions to designations promulgated in 2018 for northern Weld County, Colorado, and El Paso, Texas, as areas that had attained 2015 ozone pollution standards. The revised designations folded Weld County into the greater ...

The D.C. Circuit, in a split ruling, vacated certain provisions of EPA's rule phasing out the use of hydrofluorocarbons (HFCs). Two companies and three trade groups argued EPA exceeded its authority in issuing the rule and that the American Innovation and Manufacturing (AIM) Act, which directed the ...

The U.S. Supreme Court held, 5-4, that an 1868 peace treaty between the Navajo Nation and the United States establishing the Navajo Reservation reserved necessary water to accomplish the purpose of the reservation, but did not require the U.S. government to take affirmative steps to secure water for...

The Ninth Circuit, 2-1, denied a municipal irrigation district's request to compel a district court to remand to state court its motion for preliminary injunction in a suit concerning water allocation in the Klamath Basin. The district initially sought to stop the Bureau of Reclamation from releasin...

A district court granted in part and denied in part an environmental group's motion for summary judgment in a CWA citizen suit concerning the Forest Service's discharge of aerially deployed fire retardant into navigable waters of the United States without an NPDES permit. The group argued the Servic...

The U.S. Supreme Court held that the CWA extends to only those "wetlands with a continuous surface connection to bodies that are 'waters of the United States' in their own right," such that they are indistinguishable from those waters, in a challenge to an EPA compliance order stating that landowner...

The Sixth Circuit granted the Commonwealth of Kentucky's and business groups' motions to preliminarily enjoin EPA's and the Army Corps of Engineers' 2023 rule revising the definition of "waters of the United States" under the CWA. A district court had denied the motions, concluding plaintiffs lacked...

The D.C. Circuit vacated EPA's withdrawal of its determination to regulate perchlorate in drinking water. An environmental group argued EPA lacked the authority to withdraw the determination under the SDWA, and that even if it did have such authority, it acted arbitrarily and capriciously in doing s...

In an unpublished order, the Fifth Circuit, 2-1, stayed EPA's disapproval of SIPs submitted by Texas and Louisiana following the Agency's 2015 revision to the ozone NAAQS. The states moved for a stay pending review of EPA's disapproval. The court found a stay was appropriate because the states made ...