US President George Bush has handed the environmental movement (and the judiciary) a significant slap in the face, overruling a judge's decision not to allow the US Navy to use sonar during exercises. The US beak had issued preliminary limitations on sonar use following a lawsuit in which environmental activists said that the gear causes harm to dolphins and whales.

AP reports that the White House announced the presidential exemption on Wednesday, Mr Bush having signed the necessary documents on Tuesday while travelling in the Middle East.

"This exemption will enable the Navy to train effectively and to certify carrier and expeditionary strike groups for deployment in support of worldwide operational and combat activities, which are essential to national security," according to the White House.

Legal efforts to stop US naval units using sonar have been underway for some time now, spearheaded by environmental pressure group the Natural Resources Defence Council. The group says that active naval sonar - which is used to detect mines or submarines by "pinging" sound pulses into the sea and listening for the echoes - distresses various forms of marine life, particularly cetaceans.

"The president's action is an attack on the rule of law," the NRDC's Joel Reynolds told AP.

"By exempting the Navy from basic safeguards under both federal and state law, the president is flouting the will of Congress, the decision of the California Coastal Commission and a ruling by the federal court."

The Bush exemption reportedly allows the USN to continue using mid-frequency active sonar in waters off California, where several key naval bases are located. This kind of sonar has been in use by navies worldwide since at least the 1960s, while the sonar-effects-on-cetaceans debate is of much more recent origin.

Some have theorised that in fact it is different equipment, low-frequency active sonars - which have come into naval vogue only in recent years - which primarily affects whales and dolphins. However, the NRDC contends that all sonars cause harm.

The campaign group plans to challenge the presidential exemption in legal filings later this week. ®