Section 51 of the Constitution of Australia enumerates the legislative powers granted to Federal Parliament by the Australian States at Federation. The list contains 39 subsections, each referred to as a 'head of power' under which the parliament is empowered to make laws. The section is not an exhaustive list, as the federal parliament is authorized to enact legislation outside of those topics by certain other sections in the Constitution, such as sections 52 and 128. Australian States may still enact legislation upon the topics in section 51; but Federal law prevails to the extent of any conflict of laws. Powers of the Parliament Federation was intended to address problems caused by having the separate colonies on the one continent. Section 51 therefore encompasses a group of powers (known as heads of power) which reflect what powers the Commonwealth was viewed as needing to solve those problems. The most important heads of power in terms of supporting contemporary Commonwealth legislation are: 'the interstate trade and commerce power': s51(i) trade and commerce with other countries, and among the States: 'the corporations power': s51(xx) "foreign corporations, and trading or financial corporations formed within the limits of the Commonwealth" 'the external affairs power': s51(xxix) external Affairs: 'Taxation power': s51(ii) "taxation; but so as not to discriminate between States or parts of States": (Combined with s96 –see 'tied grants' below). Other heads of power include: Military defence: s51(vi) (see Australian Communist Party v Commonwealth for a landmark decision on the use of this power) Quarantine: s51(ix) Census and Statistics: s51(xi) Currency: s51(xii) Weights and measures: s51(xv) Service and execution of court processes: s51(xxiv) and the recognition of judgements s51(xxv) Naturalisation and aliens: s51(xix) and immigration s51(xxvii) Powers for implementation of a uniform railway system (s51(xxxiii), s51(xxxiv), and s51(xxxii)) "the acquisition of property on just terms from any State or person for any purpose in respect of which the Parliament has power to make laws"; s51(xxxi) "postal, telegraphic, telephonic, and other like services" s51(v). Pacific relations, s51(xxx) The influx of criminals, s51(xxviii) 'Special laws' for people of any race: s51(xxvi) Marriage and divorce, per s51(xxi) and s51(xxii). Social security, per s51(xxiii) and s51(xxiiiA) (an amendment – see Social Services Referendum 1946). Copyright, patents, and trade marks per s51(xviii). Bankruptcy, s51(xvii). Bills of exchange s51(xvi) Banking (other than state banking) s51(xiii) Insurance (other than state insurance) s51(xiv) Conciliation and arbitration of industrial disputes: s51(xxxv) Flexibility for