As the law forbids the actual performance of certain acts
• because opposed to social welfare, so it regards as obnoxious various executory agreements. The common law has developed on this subject as on others, a body of doctrine aside from statutory prohibition. Illegal agreements are sometimes classified as for instance, into those which are contrary to positive law, those which are contrary to morality, and those which are contrary to public policy;1 but there seems no importance to these distinctions. Except where agreements are in terms forbidden by statute, the common law, whenever it refuses to enforce them, though they comply with the ordinary requirements for the formation of contracts, so decides on the basis of public policy. The precise particulars in which an agreement may be opposed to public policy are so various that any classification intermediate between the general heading of illegal agreements and the specific headings appropriate to each species of them, seems of little value. It may be said broadly that whenever the performance of an act would be either a crime or a tort, an agreement to do that act, will also be illegal. The converse, however, is not true. Many acts which are neither criminal or tortious may not be made the subject of a contract. An agreement beforehand to do them is illegal. This is true for instance of many agreements in restraint of trade and of champertous agreements. It should be said here that when an agreement is spoken of as illegal, it is not meant thereby to assert that it is criminal or that the law will visit with any punish-ment the making of such an agreement other than refusing to enforce it. Though the making of some agreements may be criminal and punished as such, any treatment of such a question is out of place here. In this treatise the only inquiry which is appropriate is in what cases and to what extent the law denies, for reasons of public policy, the usual characteristics of contractual obligations to agreements which fulfil the technical requirements for the formation of contracts. On the other hand, when an agreement is spoken of as illegal or unlawful, something more is meant than that it is unenforceable because a required form has not been complied with, or because
1This is a division adopted by Sir Frederick Pollock, Wald'a Pollock on
Contracts (3d ed.), p. 370, though he recognises that it has Blight value.
• it is ultra vires.1a Though the power of courts to invalidate agreements of parties on grounds of public policy is unquestioned, and is obviously necessary, the impropriety of a transaction should be clear in order to justify the exercise of the power.
" If there is one thing more than any other which public policy requires, it is that men of full age and competent understanding shall have the utmost liberty of contracting, and that contracts when entered into freely and voluntarily, shall be held good and shall be enforced by courts of justice." 2