Whether plaintiffs adequately plead fraudulent concealment for tolling the Section 15b statute of limitations by alleging an unwritten agreement

Congress has provided a four -year statute of limitations for antitrust claims alleging a violation of Section 1 of the Sherman Act . See 15 U.S.C. 1 (Sherman Act), 15b ( Clayton Act statute of limitations). Like other federal limitations periods, the Section 15b stat-ute of limitations may be tolled under the doctrine of fraudulent concealment. In the decision below, t he Fourth Circuit parted ways with the Fifth, Sixth, and Ninth Circuits in holding that plaintiffs who allege a n unwritten conspiratorial agreement sufficiently plead an affirmative act of fraudulent concealment —even though nearly all plaintiffs claiming an unlawful conspiracy will be able to make such an allegation, and even though the bare assertion of an unwritten agreement does not reflect any active attempt to mislead third parties in order to con ceal the conspiracy. The question presented is: Whether plaintiffs adequately plead that defendants engaged in fraudulent concealment , for purposes of tolling the Section 15b statute of limitations, by alleging that defendants maintained an unwritten agreement.