A federal district court preliminarily enjoined efforts by the Bush administration to allow countries, such as Mexico, to label their tuna “dolphin safe” even if dolphins were chased and encircled in nets in order to catch fish swimming beneath them. More than seven million dolphins have been killed by this fishing technique, according to Earth Island Institute, one of several environmental groups challenging the 2002 decision by the Commerce Department. The court’s April 10 action reinstates the old standard -- under which imported tuna cannot be labeled “dolphin safe” if caught by using nets on dolphins -- pending the trial’s outcome.