Nov. 12 (Bloomberg) -- The U.S. Supreme Court lifted restrictions on the Navy's use of sonar during training exercises off the Southern California coast, ruling that national security needs trumped environmental concerns.

A divided high court rejected arguments by environmentalists that the judge-ordered restrictions were warranted to protect whales and other marine mammals.

The environmental interests ``are plainly outweighed by the Navy's need to conduct realistic training exercises to ensure that it is able to neutralize the threat posed by enemy submarines,'' Chief Justice John Roberts wrote for the majority.

The case tested the power of the White House and the military to skirt federal environmental regulations in the name of national security. The Bush administration argued that courts should be deferential when the president concludes that a military exercise is essential for the country's safety.

Two justices, Ruth Bader Ginsburg and David Souter, dissented, while another, Stephen Breyer, said he agreed with Roberts only in part and would have imposed more limited restrictions on the Navy. The final justice, John Paul Stevens, effectively joined Roberts on the outcome, without adopting the chief justice's reasoning.

The ruling may have limited practical impact because the Navy has already completed 13 of its 14 planned exercises. The training is designed to prepare naval strike groups for deployment in the western Pacific and Middle East.

`Great Deference'

Still, Roberts's opinion said the high court should give ``great deference'' to the president's assessment of national security needs.

``The proper determination of where the public interest lies does not strike us as a close question,'' Roberts said.

Environmental groups led by the Natural Resources Defense Council, or NRDC, sought to limit the Navy's use of mid-frequency active sonar, also known as MFA sonar, which ships use to detect submarines. The environmentalists said MFA sonar has killed and injured beaked whales and other marine mammals.

The NRDC pointed to the National Environmental Policy Act's requirement that government agencies prepare an environmental impact statement before taking harmful actions.

Ginsburg Dissent

In her dissenting opinion, Ginsburg said federal law was clear that the Navy was required to complete an environmental impact statement before beginning its training exercises.

``There is no doubt that the training exercises serve critical interests,'' she said. ``But those interests do not authorize the Navy to violate a statutory command.''

U.S. District Judge Florence-Marie Cooper limited the Navy's use of MFA sonar. Her order required the Navy to take a number of steps, including shutting down MFA sonar when marine mammals are spotted within 2,200 yards and reducing sonar power by 75 percent in the presence of a water condition known as ``surface ducting.''

The San Francisco-based 9th U.S. Circuit Court of Appeals upheld Cooper's order, though it also issued a stay that temporarily relaxed the restrictions. Today's ruling has the effect of lifting that stay.

Trade groups representing the forest products, pesticide, agricultural and home-building industries supported the Bush administration in the case.

Navy Pleased

Navy Secretary Donald C. Winter hailed the ruling.

``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,'' Winter said in a statement.

The NRDC characterized the ruling as a limited one that didn't address four other restrictions ordered by the trial judge. The Navy chose not to challenge those restrictions in its Supreme Court appeal.

``This is a narrow ruling that leaves in place four of the injunction's six mitigation measures that protect marine mammals from harm caused by high-intensity sonar during training,'' said Joel Reynolds, an attorney with the group.

The Pacific Legal Foundation, a group that supported the Navy in the case, called the ruling a ``big step forward for common sense in the law.''

The case is Winter v. Natural Resources Defense Council, 07- 1239.

To contact the reporter on this story: Greg Stohr in Washington at gstohr@bloomberg.net.

Last Updated: November 12, 2008 15:31 EST