For years corporate lawyers have tried to make the case that companies can turn over once-privileged documents to regulators without waiving the privilege when confronted by shareholder lawsuits. Court rulings have been inconsistent, but in December, Merck & Co. Inc. was slapped down hard when it tried to make that argument.

Even though the pharma giant got the U.S. Department of Justice to sign an agreement that Merck had not waived privilege when it turned over documents involving Vioxx, a federal district court ordered the company to produce those documents in the Vioxx multidistrict securities litigation.