The U.S. Supreme Court voted 5-to-4 to lift restrictions on the Navy's use of sonar in training exercises off the California coast.
The decision is a defeat for environmental groups who say the sonar can harm whales and other marine life.
The court did not deal with the merits of the environmentalists' claims.
Daniel Hinerfeld with the Natural Resources Defense Council says the Navy could monitor for marine mammals during exercises and not test in waters when the mammals are nearby.
Hinerfeld: There's no question that simple mitigations can really reduce that harm. And we strongly believe, what the lower courts found, which is that the Navy can adopt those mitigations without interfering with its training.
He says in the meantime, the NRDC will continue to work with the Navy to reduce harm to mammals when testing resumes next month.
Hinerfeld says it's possible the testing policies could change after President-Elect Barack Obama takes office.
The U.S. Supreme Court says federal courts had abused their discretion by ordering the Navy to limit sonar use in some cases and to turn it off altogether in others.
Chief Justice John Roberts wrote the majority opinion, saying the most serious possible injury from the training exercises would be harm to an unknown number of marine mammals.
But he wrote that forcing the Navy to use inadequately trained forces "jeopardizes the safety of the fleet."
Justice Ruth Bader Ginsburg wrote the dissent and said the Navy's own assessment predicted substantial harm to marine mammals.
