BP suffered another court loss this week as a federal appeals court reaffirmed a June ruling that the oil giant is liable for federal Clean Water Act damages stemming from the 2010 Deepwater Horizon explosion and subsequent oil spill.

The three-judge panel from the 5th U.S. Circuit Court of Appeals rejected BP’s argument that the June 4 decision contained errors. The oil company has said it should not be liable because an equipment failure on the Deepwater Horizon caused the maritime accident, which killed 11 people and sent millions of gallons of oil spilling into the Gulf of Mexico.

This latest ruling is not the end of the battle. BP and Anadarko Petroleum, its minority partner in ownership of the Macondo oil well, have requested that the full 15-member court reconsider the issue. That request is still pending.

They have also requested reconsideration of a ruling by U.S. District Judge Carl Barbier that found that BP was “grossly negligent.”

If the rulings from Barbier and the 5th Circuit Court of Appeals hold, it could cost BP up to $18 million in Clean Water Act penalties.