WASHINGTON — The Supreme Court justices appeared closely split Wednesday on whether the environmental laws can be used to protect whales and other marine mammals from the Navy’s use of sonar off the coast of southern California.

A Bush administration lawyer argued that when national security is at stake, the president and his top military commanders are entrusted with setting the rules.

“The ability to locate and track an enemy submarine … is vitally important to the survival of our naval strike force … and therefore, critical to the nation’s own security,” said U.S. Solicitor General Gregory Garre. For years, the Navy has conducted training exercises off the California coast to test whether ships can detect quiet-running enemy submarines. These exercises are “in the judgment of the president and his top naval officers in the paramount interests of the United States,” he added.

Garre urged the court to throw out a Los Angeles judge’s order that put limits on the Navy’s operations. Acting on a suit brought by the Natural Resources Defense Council in Santa Monica, Calif., U.S. District Judge Florence-Marie Cooper ordered the Navy to shut down its high-intensity sonar whenever a whale or marine mammal is spotted within 1.25 miles of the ship.

The sonar emits a powerful sound wave in the water — as “if we had a jet engine in this courtroom and you multiplied that noise by 2,000 times,” said Los Angeles lawyer Richard Kendall, who represented the Natural Resources Defense Council. He said beaked whales, in panic, dive deeply to escape the sound, and they sometimes suffer bleeding and even death when they try to resurface. He also cited the Navy’s own estimate that 170,000 dolphins and other marine mammals would flee the sonar.

Garre, the government lawyer, agreed some marine animals might swim away, but he disputed the claim that they would be hurt or killed. “There have been beachings of beaked whales in Southern California. None have been tied to sonar operations,” he said.

The case has turned into a major dispute over whether judges, acting on a suit brought by environmentalists, have the power to halt a government project because of its failure to carry out an environmental impact statement in advance. Judge Cooper cited this failure by the Navy when she issued her order.

On Wednesday, she came under criticism from the justices.

Justice Antonin Scalia said the law requiring environmental impact statements was “procedural” only. It did not give judges the power to stop government projects, he suggested. And Chief Justice John Roberts said that in balancing the interests, the judge did not give enough weight to the Navy’s concern. He described it as the “potential that a North Korean diesel electric submarine will get within range of Pearl Harbor undetected.”

On the other side, Justices John Paul Stevens and David Souter wondered how the Navy could know its sonar would not harm the whales until it had studied the matter. “The whole theory of the environmental impact statement is we don’t really know what the harm will be,” Stevens said.

The justices are likely to hand down a ruling in the case within a few months.