A point of controversy with regard to the antitrust agencies' treatment of accountable care organizations (ACOs) has been what joint organizations need to do to be viewed as a single entity rather than individuals conspiring on contracts. The FTC and DOJ gave a fairly clear answer on this: If the ACO meets CMS eligibility criteria, the antitrust agencies will consider it to be clinically integrated for their purposes. But guidance is lacking about what would happen with the ACO's arrangements with private health plans if at some point the ACO stops participating in Medicare. “At that point you lose any protection under this guidance,” says Brent Rawlings, an attorney at McGuire Woods. “If your contract with a private payor doesn't involve financial risk or if you're not clinically integrated independent of your participation in Medicare, then you face some significant antitrust issues.”