Group boycotts are per se antitrust violations only if the boycott cuts off access to a supply, facility, or market necessary to enable the boycotted firm to compete, the group possesses a dominant position in the market, and the boycott is not justified by a plausible argument that it is intended to enhance overall efficiency and make markets more competitive. Here, the plaintiff journalists did not allege that defendant’s membership rules cut off plaintiffs’ access to a supply, facility or market. Members’ greater access to Hollywood stars is governed by movie companies, not the association, and the association lacks market power. And the Supreme Court has cautioned against easily deeming professional association activities or rules per se antitrust violations. Plaintiffs also failed to allege a per se violation of market division since the complaint alleged each country was a separate sub-market, rather than that there was a single unified market for foreign reporting about movies. If members reporting to different countries were not in the same market, the association’s rules forbidding one from reporting in the other’s country did not divide any market in which the two members both participated. The plaintiffs failed to allege a rule of reason antitrust violation because the association lacked market power in any reasonably defined market. Plaintiffs also failed to allege a claim under California’s common law right to fair procedures by a private organization in admitting or expelling members. That right applies only to private organizations that affect the public interest and are quasi-public. The association is not such an organization.