The basic principle of Australian contract law is freedom of contract, under which parties are at liberty to strike whatever bargain they choose. A v Hayden (1984) 156 CLR 532.Illegality - contracts prejudicial to administration of justice. This site is designed to provide an introduction to Australian contract and consumer law. Two major problems are identified with the current law. A business contract is a legally binding agreement between two or more persons or entities. Contracts can be complex.