Seattle -- A federal appeals court ruled Friday that the Makah tribe could not resume gray whale hunts, agreeing with whaling opponents who argued that the government must study the hunt's effects more thoroughly.

A 9th Circuit Court of Appeals panel in San Francisco rejected as inadequate a federal environmental assessment showing the hunt had no significant effect. The court said the assessment did not adequately determine the hunt's effect on the local whale population and the precedent the hunt could set in other areas.

Questions remain "as to whether the tribe's whaling plans will have a significant effect on the environment," said Judge Marsha Berzon, writing for the panel.

Overturning a lower court, the panel ordered the National Marine Fisheries Service to create an environmental impact statement, a document more extensive than an environmental assessment.

"We are extremely excited about the court's decision," said Michael Markarian, president of the Fund for Animals.

A lawsuit filed by the New York-based group, the Washington, D.C.-based Humane Society of the United States and others contends that Makah whaling would endanger public safety and harm gray whales that linger in Washington's Strait of Juan de Fuca. The bulk of the population migrates between Alaska and Mexico.

"Clearly, we're disappointed," Fisheries Service spokesman Brian Gorman said. But he added that the agency probably would heed the court's order.

The tribe's lawyer, John Arum, said Friday he had not read the court's opinion and could not comment. Calls to the Makah tribal chairman were not immediately returned.

Makah whaling rights are guaranteed by an 1855 treaty.