In City of Columbia v. Omni Outdoor Advertising, Inc. (1991) 499 U.S. 365, the court examined whether an antitrust claim (as well as a subsidiary state law claim) could be pursued against city officials and private actors when the gravamen of the agreement or conspiracy was that the private actor had conspired with local officials to adopt legislative enactments that restrained trade and monopolized the market. The Supreme Court reaffirmed the plaintiff could not state a Sherman Act claim against the city because of the Parker immunity doctrine (Parker v. Brown (1943) 317 U.S. 341), and specifically rejected the plaintiff's argument that the Parker immunity could be forfeited if the plaintiff could prove the politicians had conspired with private actors to create the restraint of trade, declaring "there is no such conspiracy exception" to the Parker immunity doctrine. (City of Columbia, supra, 499 U.S. at pp. 374-375.) Moreover, the Supreme Court considered the plaintiff's argument that a conspiracy exception "limited to instances of governmental 'corruption' " should be recognized and, for a variety of reasons, rejected that argument. (Id. at pp. 376-379.) City of Columbia then considered the antitrust liability of the private actors who allegedly conspired with the public officials to induce passage of the anticompetitive legislation. The Supreme Court reaffirmed the general rule that concerted efforts to influence public officials do not give rise to liability under antitrust laws because of the Noerr-Pennington immunity. After concluding the private actor is protected by Noerr-Pennington immunity (Eastern R.R. Presidents Conference v. Noerr Motor Freight, Inc. (1961) 365 U.S. 127; United Mine Workers of America v. Pennington (1965) 381 U.S. 657.) and the "sham" exception was inapplicable, the Supreme Court examined whether "we should use this case to recognize another exception to Noerr immunity--a 'conspiracy' exception, which would apply when government officials conspire with a private party to employ government action as a means of stifling competition." (City of Columbia, supra, 499 U.S. at p. 382.)