In a rare boost for securities fraud class actions, the U.S. Supreme Court on Tuesday closed off a “statute of limitations” defense for Merck & Co. in its battle against Vioxx-related shareholder suits.

The Court unanimously ruled in Merck v. Reynolds (pdf) that the litigation is timely and must go forward, in spite of Merck’s insistence that the suit was filed too late under the two-year statute of limitations contained in the Sarbanes-Oxley Act of 2002.