U.S. District Judge Florence-Marie Cooper agreed with the NRDC that use of the mid-frequency sonar would create a "near certainty" of harm to the mammals. In January of this year, she handed down an order that limited the Navy's use of sonar when marine mammals came within 2,200 yards of a vessel. She said sonar could not be used with 12 miles of the coast, nor near the Catalina Basin, where whales congregate.
Navy leaders took particular exception to the requirement to power down the sonar whenever the mammals came within 1.25 miles of a ship.
"Imposing that restriction means a complete loss of training in that environment," Vice Adm. Samuel J. Locklear, commander of the U.S. 3rd Fleet in San Diego, said Monday. "It would effectively eliminate any productive anti-submarine rehearsals."
In February, the U.S. 9th Circuit Court of Appeals upheld Cooper's order but modified it somewhat. During a "critical point" in a training exercise, the Navy may use the sonar at a lower decibel level even when mammals are spotted within a mile of the ship, the appeals court said.
But the administration appealed on behalf of Navy Secretary Donald C. Winter and said that even the modified order "jeopardizes the Navy's ability to train sailors or Marines for wartime deployment during a time of hostility."
The judge's order appears to stand on a weak platform, the administration lawyers said.
It rests on an alleged violation of the National Environmental Policy Act, which requires the government to conduct environmental impact studies.
That law does not forbid the government from taking action, they said.
Separately, the Marine Mammal Protection Act protects whales and other marine mammals, but it includes an exception for "military readiness activity." And in this case, the Defense Department exempted the Navy from complying with this measure during its California training exercises.
Lawyers for the NRDC said they were not surprised by the court's willingness to hear the Navy's appeal but said they remained confident of winning.
Richard B. Kendall, a Los Angeles lawyer who represented the NRDC, pointed out that the justices had recently rejected a similar claim from the administration that the military's need to hold "enemy combatants" at Guantanamo Bay trumps the detainees' right to go to court.