Facing accusations by the city of Chicago that they hid the truth about addictive painkillers, a quintet of drug companies took aim at the city’s decision to hire a private law firm, Cohen, Milstein Sellers & Toll, to prosecute the case. But Cohen Milstein beat back the drugmakers’ attacks for a second time on Monday, when a judge ruled that Chicago hadn’t improperly ceded its “police power” to the firm.

Rejecting arguments by OxyContin manufacturer Purdue Pharma Inc. and other defendants, U.S. District Judge Jorge Alonso refused to unwind the partnership between Chicago’s corporation counsel and Cohen Milstein, which serves as outside plaintiffs counsel in the city’s lawsuit alleging that several drug companies engaged in “highly deceptive” marketing of opioid painkillers.