In another victory for common sense, the Supreme Court has upheld the right of the Navy to practice the use of sonar off the coast of Southern California.

The National Resources Defense Council had sued the Navy to block the use of sonar in that area, contending that the acoustic signals might damage whales and other marine mammals.

Sonar is used to detect submarines. It sends out sound waves and analyzes the patterns coming back from anything under water. Modern submarines are extremely quiet, so sonar is about the only way to detect them and to defend a fleet of surface ships against submarine attacks.

Chief Justice John Roberts wrote the ruling for the majority. He weighed the relative risks. On the one hand, the sonar waves might cause discomfort or disorient an unknown number of marine mammals. "In contrast, forcing the Navy to deploy an inadequately trained anti-submarine force jeopardizes the safety of the fleet."

The right-thinking justices who joined his opinion were Samuel Alito, Anthony Kennedy, Antonin Scalia and Clarence Thomas.

John Paul Stevens wrote a separate opinion citing procedural points. Stephen Breyer would have allowed some of the anti-sonar restrictions to remain. And Ruth Bader Ginsburg and David Souter said potential harm to the whales was sufficient to justify limits on the use of sonar.

In the starkest terms, the choice was between the fate of U.S. sailors in case of war and the fate of whales.

Five members of the court decided in favor of the sailors over the whales. We should be grateful to the five - but only five?

The case highlights the stakes when our new president names a replacement for the next vacancy on the court. (hh)