12.
Appeal was not asked, and did not decide, whether the obligation should properly be so characterised.
39 The reasoning by which the Court of Appeal reached that conclusion essentially involved three steps. The first was to accept that, by providing in s 17(4) of the Casino Act that the CDA operates as a deed, the South Australian Parliament indicated that the general law of contract will apply to the CDA except to the extent modified by statute. The second was to invoke the "general proposition" that a statute "is not to be interpreted as withdrawing or limiting a conferral of jurisdiction unless the implication appears clearly and unmistakably",[1] in order to postulate that a clear and unmistakeable manifestation of legislative intention needed to be found in the Casino Act in order to oust the common law and equitable jurisdiction of the Supreme Court to declare a provision of the CDA unenforceable as a penalty. The third was to postulate that, although such a clear and unmistakeable intention is manifested in the specific references in ss 17(1)(c) and 51 of the Casino Act to "penalties", it cannot be found in the references in those same provisions to "interest".[2]
40 This reasoning inverts the scheme of the Casino Act. The CDA is an agreement that is authorised and required by statute to govern the imposition of a tax – a compulsory exaction of money by a public authority for public purposes. The imposition of a tax is a topic that is inherently and exclusively statutory,[3] and so that topic is treated within the scheme of the Casino Act. The agreement that can be entered into between the licensee and the Treasurer in the CDA is limited to an agreement that deals with specific matters in s 17(1)(a), (b) and (c) purposively construed within the context of the Casino Act. The enforceability of the agreement in fact entered into by the licensee and the Treasurer in the CDA within the scope of one or more of those obligations is governed by other provisions of the Casino Act.
41 Section 51(1) operates in combination with s 51(4) to permit an agreement to pay casino duty, within the scope of the description in s 17(1)(b), or to pay interest or penalties for late payment or non-payment of casino duty, within the
