The right to petition protects efforts to influence government action from liability, most prominently under the antitrust laws but extending to other claims.

Scope. Lobbying legislatures and agencies, litigation and threats of litigation, and participation in administrative proceedings — including where the purpose is to disadvantage a competitor.

Sham exception. Protection is lost where the petitioning is a sham: the lawsuit or petition is objectively baseless, such that no reasonable litigant could expect success, and it is subjectively motivated by an intent to interfere directly with a competitor’s business through the process itself rather than through the outcome.

Series of claims. Where a party files many proceedings, some courts assess whether the series was brought without regard to merit rather than testing each one.

Beyond antitrust. Courts have applied the doctrine to tortious interference, unfair competition and other claims arising from petitioning conduct.

Fraud on the tribunal. Misrepresentations to an agency or court may forfeit protection.

Where it matters commercially. Objections to a competitor’s permit application, participation in a rezoning hearing, standards-setting activity, and litigation between competitors. A party advised that opposing a rival’s approval is unlawful interference is usually being advised wrongly.