The U.S. Supreme Court has declined to review an August lower-court ruling favoring the San Diego Convention Center in an antitrust lawsuit brought against center operators.

Chicago-based United National Maintenance Inc. (UNM), a vendor of trade show cleaning services, sued the San Diego Convention Center Corp. in November 2007, after center officials adopted a policy in July of that year mandating that the city-appointed corporation would be the exclusive provider of cleaning services staffing within the facility.

The suit alleged interference with contractual relationships and “prospective economic advantage,” as well as antitrust violations. In May 2011, the original U.S. District Court trial jury awarded UNM damages of $668,905 on the claim regarding intentional interference with contractual relations, but did not reach a verdict on remaining claims.

The convention center filed a motion for a new trial, and the district court later dismissed UNM’s claims for interference with prospective economic advantage. The court also found that UNM failed to present sufficient evidence related to its antitrust claims.

UNM appealed to the Ninth Circuit Court of Appeals, which in August 2014 denied its petition for a rehearing, ruling that the non-profit center corporation operates publicly as an instrument of the city and is not subject to antitrust claims.

Convention center officials said the Supreme Court’s decision not to review the case means that UNM’s antitrust claims are now settled, and there is no longer any exposure for triple damages, attorney’s fees or punitive damages. The remaining claim, for intentional interference of contract, provides only for single compensatory damages.

The case is scheduled to be returned to Judge Anthony J. Battaglia in the U.S. District trial court for further proceedings on March 13, unless an earlier status conference is requested, officials said.