This chapter considers the areas in which the operation of the common law impacts upon issues that are closely related to the public regulation of competition. Certain doctrines of common law may be applied to situations in which competition is being restrained, or to competitive conduct. Common law doctrines in antitrust are becoming less important following the growth of modern competition law. The restraint of trade doctrine remains vibrant, and is often relied on in professional disputes. Restraint of trade is a doctrine of contract law under which certain contracts are unenforceable if they unreasonably restrain the activity of a party after the termination of the main contract. A number of rarely used torts may also be relevant to certain competitive situations.