Antitrust law's Walker Process doctrine permits a patent infringement defendant to show that an improperly maintained infringement action constitutes unlawful monopolization or an unlawful attempt to monopolize. The infringement defendant must show both that the lawsuit is improper, which establishes the conduct portion of the violation and generally satisfies tort law requirements, and also that the structural prerequisites for the monopolization offense are present. The doctrine also applies to non-patent infringement actions and has been applied by the Supreme Court to copyright infringement actions. Walker Process itself somewhat loosely derives from the Supreme Court's Noerr-Pennington line of cases holding that while the right to file a lawsuit is grounded in First Amendment concerns, the right does not extend to "baseless" litigation. The doctrine has not been particularly effective, however, mainly because patent boundaries are so poorly defined that it is often impossible to say that an infringement suit was baseless.
Hovenkamp, Herbert J., "The Walker Process Doctrine: Infringement Lawsuits as Antitrust Violations" (2008). Faculty Scholarship at Penn Law. 1784.