A federal appeals court in San Francisco allowed to US Navy to continue using sonar technology that scientists have linked to mass die-offs of whales.

Earlier this month, US District Judge Florence-Marie Cooper has pronounced a temporary injunction in response to a US Navy demand to dismiss a lawsuit initiated by the Natural Resources Defense Council (NRDC).

NRDC claimed that the US Navy had 14 training exercises to take place in the waters off Southern California, an area rich in marine life, using the harmful mid-frequency sonar.  NRDC stated that this technology, by flooding large areas of the ocean with loud burst of sounds, causes injures or even whales’ strandings.

On Friday, the 9th Circuit US Court of Appeals ruled that US District Judge Florence-Marie Cooper did not give adequate consideration to the public's interest "in having a trained and effective Navy." The appeal court ruled 2-1 in the favor of the US Navy.

"The safety of our whales must be weighed, and so must the safety of our warriors. And of our country," wrote Circuit Judge Andrew Kleinfeld, joined by Judge Consuelo Callahan.

“The public does indeed have a very considerable interest in preserving our natural environment and especially relatively scarce whales. But it also has an interest in national defense. We are currently engaged in war in two countries,” wrote Judge Andrew Kleinfeld.

The U.S. Navy’s argument for the necessity of such use is that the proliferation of silent diesel-electric   submarines from many countries, including North Korea and Iran, puts in jeopardy the national security.

“The ability to detect and track potentially hostile submarines is a critical skill that cannot be duplicated in the classroom or by simulation,” said Capt. Scott Gureck, a Navy spokesman.

The Navy added that it has already taken into consideration curbing the effects the sonar might have on the marine mammals and that, during the 3 training exercises that had already taken place, no strandings or behavioral disturbance were reported.

Dissenting judge, Milan D Smith, wrote that the Navy did not make a compelling case for how national security would be jeopardized and that the lawsuit filed against the Navy by the Natural Resources Defense Council to stop the Navy's unmitigated use of the sonar is likely to win.

"Unlike my colleagues in the majority, I am satisfied that the district court carefully weighed national security and public interest considerations before issuing the preliminary injunction in this case," he wrote.

Smith added the Navy was free to use the sonar outside of Southern California waters.

A further hearing is to be scheduled in the near future for the court to hear more detailed arguments.

"This is a short-term stay to allow the court to review the merits in full," said Joel Reynolds, senior attorney at the NRDC. "The court will hear the matter on a highly expedited basis, and we look forward to that review."