Certain contracts which are regarded by the courts as obviously and seriously inimical to the interests of the state, as well as all contracts forbidden by the legislature, are said to be illegal. Statutory prohibitions are occasionally so construed as not wholly to invalidate, or render unenforceable, contracts entered into in violation of their provisions,1 but as a general rule illegal contracts, although entered into by competent parties and possessing all of the internal essentials of validity, do not give rise to contractual obligation. The purpose of this chapter is to consider the quasi contractual obligation resulting from the part performance of contracts unenforceable because of illegality.1

1 A conspicuous example is the case of ultra vires contracts of corporations. See post, Sec. 154 et seq.