After two pipe bombs damaged their buildings in 2003, and after employees had been repeatedly harassed at their homes by animal rights activists wielding bullhorns and sirens, Chiron Corp. decided enough was enough. The Emeryville, Calif., biopharmaceutical company last year filed a lawsuit against the activists. They won a preliminary injunction restricting their protests. "When all the activity against us began, we thought if we kept our head down, it would go away," says Chiron spokesman John Gallagher. "In fact, it did not." Since winning the injunction, he said, "it's been pretty quiet."