Abstract: This essay sketches a new approach to ameliorating the problem of coordinating the use of private class actions and public policing to enforce American antitrust law. Achieving the optimal joint level of enforcement from any system that teams public and private law enforcers requires a coordination mechanism to assure not only that each makes the appropriately motivated and proportionate investment of resources and effort, but also that their respective litigation and settlement decisions are properly synchronized and combined. Our proposal addresses this double-sided coordination problem with a sequential enforcement mechanism. In essence, the system would work as follows: (i) total enforcement license initially vests with the public enforcer; (ii) public enforcer auctions private license to enforce a mandatory-litigation class action; (iii) winning bidder retains recovery from class judgment or settlement; (iv) auction proceeds are deposited with and immediately distributed by the court for compensatory purposes; and (v) public enforcer has option to buy back the private license at the winning bid price. Our approach is superior to the current judicial methods of coordination, which are undertaken through a process of applying doctrines of pre-emption, statutory interpretation, and class action prerequisites. These judicial methods are haphazard and are hampered by courts' information deficits. Our approach is also preferable to proposed statutory reforms that would give public authorities exclusive power to prosecute or terminate the class action on their own, or to intervene and exert some control over private enforcement actions. Our approach affords public enforcers these same options to control the use of class actions. Unlike our approach, however, such reform proposals make no attempt to deal with the problem of giving public authorities appropriate incentives in the decision whether to interfere with private enforcement actions.