No doubt, this Act does tend to encourage employers who pay fair wages to their employés; and it was meant to do so. Therefore, with our limited experience of the working of a federal system, our first and superficial impressions must be adverse to the constitutionality of the Act. "This is," we say, "an attempt of the Federal Parliament to regulate wages. Wages are a matter for the State Parliament only; why should the Federal Parliament be meddling with what is not its business?" Yet in this short argument there are two misleading expressions. Every one agrees that if this Act regulates wages, in the sense of prescribing wages, commanding what wages shall be paid, making it illegal, in any sense, to pay other wages, the Act is, to that extent, void. But it is competent for the Federal Parliament to use any of its admitted powers in such a manner as to affect or influence the rate of wages, however materially. The truth is that, where two law-making powers operate over the same territory and the same people, the laws of one authority must necessarily touch, at every point, the subjects committed to the other authority, and must frequently affect the conduct of persons with regard to those subjects. It would profoundly affect the exercise of the State powers with regard to State subjects if the Federal Parliament were to prohibit the importation of foreign books, to forbid inter-state carriage of cattle, or the export of wool, or the import of scientific apparatus, to sweep away all lighthouses, to abolish the marriage tie, to prescribe that all infants shall be sent to the custody of certain institutions. The electors would have something to say as to such legislation; but its influence on State businesses, State education, State railways, State morals, or State solvency, would not make it void. It is true that, if the Federal Parliament can make its taxation depend on the scale of wages paid by an employer, it can make its taxation depend upon other things - the length of each man's foot, his abstinence from tobacco and beer, the number of his children; or it can impose a licence fee on all persons carrying on a specified trade, with remission to those who carry on under specified conditions. But it is idle to say that neither the Convention nor the British Parliament intended such things. Of course it did not; but it intended that the Federal Parliament should be free to deal with federal subjects as it thought best for the people of Australia - it did not intend that the Federal Parliament should move in leading strings. The mere fact, therefore, that the Federal Parliament lays down certain unusual conditions as to wages in a taxation Act does not make that Act void, provided that it does not purport to regulate wages in the sense of making a law, a legislative command, to pay wages. The second fallacy lurks in the statement that wages are a matter for the State Parliaments only. It is true that the Federal Parliament has no power to make laws prescribing wages. But, in the exercise of its admitted powers, the Federal Parliament may - indeed, must - often touch wages incidentally; and, if and so far as the federal law is within the admitted powers, it is valid, no matter what the State laws may say (Constitution, sec. 109). To say that the Federal Parliament cannot make a law because legislation on the subject belongs to the States is rather to invert the true position. The Commonwealth has certain powers, and as to those powers it is supreme; the State has the rest. We must find what the Commonwealth powers are before we can say what the State powers are. The Federal Parliament has certain specific gifts; the States have the residue. We have to find out the extent of the specific gifts before we make assertions as to the residue. The question, then, is merely what is the extent of this power of taxation given to the Federal Parliament, and how far may the power be applied? It is not contended for the Federal Parliament, as was contended, it seems, for the magistrates in Rossi v. Edinburgh Corporation[74], that it has power to amplify its powers, and to prescribe all that may seem to be "desirable or expedient" as an addition to its powers. It is merely contended that what has been done in this Act is within the plenary power of taxation actually granted. Now, by section 51 of the Constitution, the Parliament has, subject to the Constitution, "power to make laws for the peace, order, and good government of the Commonwealth with regard to ... taxation; but so as not to discriminate between States or parts of States." So the Parliament has, primâ facie, power to tax whom it chooses, power to exempt whom it chooses, power to impose such conditions as to liability or as to exemption as it chooses. But the Constitution expressly forbids discrimination between States or parts of States; and, according to the dictum of the High Court in Federated Amalgamated Government Railway and Tramway Service Association v. New South Wales Railway Traffic Employés Association[75], the Federal Parliament has no power to tax State officers or State agencies. Subject to this latter implication, which has been based on the nature of the Constitution, there is only one limitation - the Parliament must not discriminate between States or parts of States. The fact that this limitation is expressed excludes all limitations by implication: expressio unius exclusio alterius. With the qualifications which I have mentioned, (and certain others immaterial for the present purpose: see secs. 92, 99, 114, 117), the taxing power of the Federal Parliament is plenary and absolute; unlimited as to amount, as to subjects, as to objects, as to conditions, as to machinery. "If the right to impose the tax exists, it is a right which in its nature acknowledges no limits": Weston v. Charleston[76]; McCray v. United States[77]. This position also has not been disputed by the defendants - at all events, expressly.