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    LOS ANGELES, Feb. 4 (Xinhua) -- A federal judge on Monday rebutted President George W. Bush's order to exempt the Navy from environmental laws limiting the use of sonar off the California coast.

    In a 36-page order, U.S. District Judge Florence-Marie Cooper rejected Bush's argument that the Navy could be exempted from the federal environmental laws because of an urgent need to properly train its sailors to detect quiet submarines.

    Cooper said Bush overstepped his authority by doing so.

    Last month, President Bush signed a waiver that enabled the Navy to continue using mid-frequency active sonar, saying the Navy's training exercises were "essential to national security."

    Environmentalists led by the Natural Resources Defense Council (NRDC) believe the high-intensity sound waves hurt dolphins, whales and other marine mammals, causing them to beach themselves in some cases. According to the NRDC, some Navy sonar systems generate underwater sound waves as loud as 235 decibels.

    On Monday, Cooper wrote that the Navy failed to state exactly what was the emergency that made the waiver necessary.

    But while she expressed "significant concerns" about the constitutionality of Bush's exemption, she avoided ruling on it, saying there was a statutory reason to uphold her previous injunction.

    The judge issued the preliminary injunction on Jan. 3, ordering the Navy to stop using sonar when marine mammals are within 2,200 yards, and to monitor its test area for one hour before tests to make sure no marine wildlife is in the area.

    Cooper's ruling enabled the Navy to hold exercises within 12 miles of the mainland. Two weeks later, Cooper ordered the Navy to lower its sonar to six decibels if a marine mammal is detected within 1,000 meters.

    But she left intact a no-sonar zone between Santa Catalina and San Clemente islands off the California Coast, as well as the no-sonar buffer zone that extends 12 nautical miles from the mainland.

    Environmentalists argue that sonar noise disorients whales, causing them to become stranded on beaches and die.

    They claim the Navy has refused to take simple measures, such as avoiding whale migration routes, to reduce the environmental harm from 14 exercises planned through January 2009 that would use high-intensity, mid-frequency sonar.

    Joel Reynolds, a senior attorney for the NRDC, hailed Cooper's decision on Monday. "We're very pleased," he said. "I've always thought the president's actions were illegal in this case, and the judge has affirmed that point of view with this decision today."