affirmative defense anti-competitive practices barriers to entry bid rigging cartel case law clayton antitrust act coercive monopoly collusion competition law competition regulator conscious parallelism copyfraud copyright copyright infringement dividing territories essential facilities doctrine exclusive dealing federal trade commission act group boycott hart-scott-rodino antitrust improvements act history of competition law injunction international competition network irish competition law license market power merger control merger guidelines monopolization natural monopoly noerr-pennington doctrine patent misuse predatory pricing price fixing product bundling refusal to deal relevant market robinson-patman act rule of reason sherman antitrust act small but significant and non-transitory increase in price unclean hands united states united states court of appeals for the fourth circuit united states antitrust law