The Supreme Court refused to hear two separate cases filed by BP and Anadarko Petroleum challenging fines related to the 2010 oil spill in the Gulf of Mexico.

The nation's highest court let stand a decision from a circuit court of appeals in New Orleans, which in June 2014 said the companies are liable for penalties under the Clean Water Act.

The cases filed against the federal government by BP and Anadarko were Nos. 14-1217 and 14-1167, respectively. Anadarko held a minority stake in the Macondo well beneath the Deepwater Horizon rig in the Gulf of Mexico.

Carl Barbier, the judge overseeing the case in the U.S. District Court of the Eastern District of Louisiana, ruled BP released 3.2 million barrels of oil into the Gulf of Mexico in 2010, about 1 million barrels less than the government estimated.

His ruling left BP facing a maximum $13.7 billion fine, down from the maximum $18 billion for violations of the Clean Water Act.

The district court in Louisiana ruled in September that BP's activities at the Macondo well beneath the Deepwater Horizon rig in the Gulf of Mexico amounted to willful misconduct. In its 152-page ruling, the court found a series of BP failures at the well "created the catastrophic situation" that led to the 2010 spill.

BP last year said it would appeal the Louisiana decision. The company said the judge in the case based the decision on information that BP said he initially said he wouldn't consider in court.

There was no comment on the Supreme Court's decisions from either company.

The incident left 11 rig workers dead and led to the worst offshore oil spill in U.S. history.