SAN FRANCISCO – A federal judge has upheld the current definition of the “dolphin-safe” tuna label and barred the Bush administration from altering it, handing a victory for environmentalists.

The ruling Thursday by U.S. District Judge Thelton Henderson prevents the government from labeling tuna “dolphin safe” if fishermen encircled the dolphins to make the tuna catch.

Henderson upheld the old definition, under which any tuna caught using dolphins as targets were automatically barred from bearing the consumer-friendly label on cans sold in the United States.

On Dec. 31, the Commerce Department said tuna that fishermen catch by encircling dolphins may immediately be imported into the United States and bear the dolphin-safe label if observers certify no dolphins were killed or seriously injured in the process. Environmentalists sued.

“This is a victory for dolphins,” said Mark Palmer, spokesman for the Earth Island Institute’s International Marine Mammal Project. “We can now go to trial over the next few months knowing that the integrity of the dolphin-safe tuna label will be protected by this injunction.”

Environmentalists charged that the government failed to adequately address the stress to dolphins caused by chasing them with speedboats, encircling them in large nets and releasing them after they were caught with the tuna.

The government said less than 5,000 dolphins are killed annually using the practices in Latin America and elsewhere, down from more than 100,000 killed per year in the 1980s.

A change in the rules was strongly backed by fisheries in Mexico and Venezuela. But the government agreed not to activate it pending the judge’s decision.