San Jose U.S. District Judge Ronald Whyte has yet to make up his mind on who will take charge of one of the largest securities class actions in the country.

But he did decide two things last week in what might be a $1 billion case against McKesson HBOC Inc. First, he joined a trend among federal judges and ruled that so-called aggregation of plaintiffs into one group so as to win lead counsel status is verboten.