In the case of City of Columbia et al. v. Omni Outdoor Advertising, Inc., 1990, the Supreme Court ruled in favor of the city and its co-defendant, affirming that they were immune from federal antitrust liability under Parker v. Brown's state-action immunity doctrine. The plaintiff, Omni Outdoor Advertising, had accused them of conspiring to monopolize the local billboard market by passing an ordinance restricting new billboards' construction while exempting existing ones. However, Justice Scalia wrote for a unanimous court that even if this was true and it did result in anti-competitive effects as alleged by Omni Outdoor Advertising; such conduct is not subject to Sherman Act scrutiny when it is "clearly articulated and affirmatively expressed as state policy" which was done here through legislation enacted by elected officials.

In the dissenting opinion for City of Columbia et al. v. Omni Outdoor Advertising, Inc., Justice Stevens argued that the majority's decision to grant immunity from federal antitrust laws to local governments and private parties acting in concert with them was a misinterpretation of Parker v. Brown (1943). He contended that this ruling would allow state-sanctioned monopolies to flourish without any checks or balances, undermining competition and harming consumers. Furthermore, he expressed concern over how the court's decision could potentially shield corrupt practices under the guise of "state action." According to him, such an interpretation is inconsistent with both precedent and policy objectives underlying antitrust legislation - promoting competition and preventing economic concentration.