The Supreme Court ruled on Wednesday that the U.S. Navy's need to conduct realistic training with active sonar outweighs the concerns of environmentalists that the sonar could damage marine life.
The decision means the Navy can go forward with exercises off the coast of Southern California and does not have to sharply limit sonar use.
Chief Justice John Roberts began the opinion by quoting George Washington: "To be prepared for war is one of the most effectual means of preserving peace."
"This case was vital to our Navy and nation's security, and we are pleased with the Supreme Court's decision in this matter," the Hon. Donald C. Winter, Secretary of the Navy, said Wednesday. "We can now continue to train our sailors effectively, under realistic combat conditions, and certify our crews "combat ready" while continuing to be good stewards of the marine environment."
But Roberts, who was joined in full by Justices Antonin Scalia, Anthony Kennedy, Clarence Thomas and Samuel Alito, also wrote, "Of course, military interests do not always trump other considerations, and we have not held that they do. In this case, however, the proper determination of where the public interest lies does not strike us as a close question."
The Natural Resources Defense Council, which brought the case, pointed out that the ruling is narrow enough that it leaves several principles in place to protect the animals from the effects of the sonar.
"The Supreme Court eliminated two of the injunction's mitigation measures out of deference to the Navy's claims that they would impinge on training," Joel Reynolds, NRDC's marine mammal program director said in a statement. "The court did not upset the underlying determination that the Navy likely violated the law by failing to prepare an environmental impact statement."
Environmentalists had conveyed fear that the court's decision could set a dangerous precedent, affording the government a blank check for the use of sonar, but NRDC attorney Richard Kendall, who argued the case before the Court, expressed some measure of relief.
"It is gratifying that the court did not accept the Navy's expansive claims of executive power, and that two-thirds of the injunction remain in place," he said.
In court, Kendall had argued that there is scientific evidence that mammals such as the endangered beaked whale suffer irreversible damage when they are exposed to the intense underwater noises that sonar produces.
"The reason that happens, especially to beaked whales, is because they dive for very long periods of time," Kendall told the court. "If they come up too fast, they get the bends so there is evidence of -- when they do the necropsies of these beaked whales, they find hemorrhaging, the embolisms in various parts of the bloodstream and many, many deaths."
Kendall said the sound intensity of the sonar, correcting for water, would compare to a jet engine in the courtroom multiplied 2,000 times. He said the Navy is "perfectly able to train" with some restrictions that would protect marine life.
But the court said that while it "does not question the seriousness" of the environmentalists' concerns, the use of sonar "is the only reliable technology for detecting and tracking enemy diesel-electric submarines."
The Navy has conducted training exercises off the Southern California coast for more than 40 years. It argues that its current training exercises have taken on added significance since the United States has been engaged in ongoing hostilities.
Justice Ruth Bader Ginsburg, joined in dissent by Justice David Souter, wrote that the "likely harm," including 170,000 behavioral disturbances and 8,000 instances of temporary hearing loss among mammal life, "cannot be lightly dismissed, even in the face of an alleged risk to the effectiveness of the Navy's 14 training exercises." ABC News' Luis Martinez contributed to this report.