The following types of agreement are among those that have been held to be contrary to public policy, and therefore illegal at common law.

• Contracts involving the commission of a crime or tort
• Contracts excluding the jurisdiction of the courts
• Contracts which prejudice the administration of justice
• Contracts in restraint of trade
• Contracts to defraud tax authorities
• Contracts that promote conflict with public duties
• Contracts promoting sexual immorality

Note: This list is sufficient for introductory purposes but, for more detail, refer to any standard textbook on contract law.