The Supreme Court appeared divided Wednesday over judges' authority to limit the Navy's use of sonar to protect whales.
The court heard arguments in a dispute between the Bush administration and environmental advocates over court rulings that restrict sonar in naval training exercises off the coast of Southern California.
The administration says the training is vital for teaching sailors how to find enemy submarines.
"I see an admiral come along and say you have to train under these circumstances," Justice Stephen Breyer said. "I'm very nervous about it."
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Sonar can interfere with whales' ability to navigate and communicate. There is also evidence that the technology has caused whales to strand themselves on shore.
Richard Kendall, representing the Natural Resources Defense Council, told the justices that the Navy is managing under the restrictions, noting that eight of 14 planned exercises have been completed since the restrictions took effect.