Environmental groups are praising a federal appeals court decision that called for tighter restrictions on the U.S. Navy's use of sonar that harms whales and other marine life.
A three-judge panel of the Ninth Circuit Court of Appeals in San Francisco ruled unanimously late Friday that federal rules "did not give adequate protection to the world's oceans."
The Navy uses powerful low-frequency sonar to detect increasingly quiet foreign submarines over hundreds of miles. But the intense sonar waves are known to harm whales, dolphins, walruses, and other marine animals that rely on perception of underwater sounds.
The court said the rules, drawn up by the National Marine Fisheries Service under a law passed by Congress, were not properly fashioned to meet the law's requirement of "least practicable adverse impact" on marine life.
"The Navy got a virtual blank check to operate in more than 70 percent of the world's oceans, as if devoid of marine life," said Michael Jasny of the Natural Resources Defense Council, one of the groups that sued to block the current sonar rules.
Watch: U.S. Navy vs. The Whale
Exposure to the powerful sonar signals can cause marine animals to stop communicating and foraging for food, to separate from their offspring, and to interrupt mating.
"We have every reason to believe that the Navy has been deliberate and thoughtful" in following the federal regulations, the ruling said. But the court said the agency that drew them up did not go far enough in protecting marine mammals.
"The result is that a meaningful proportion of the world's marine mammal habitat is under-protected," it said.
The decision reversed a lower court judge's ruling in 2012 that approved the rules for a five-year period, covering peacetime operations in the Pacific, Atlantic, and Indian Oceans and the Mediterranean Sea. Friday's decision sent the case back to the judge to consider more restrictive sonar rules.
A Justice Department spokesman was not available to address the government's next legal steps.