Section 51(i) of the Australian Constitution

Section 51(i) of the Australian Constitution enables the Parliament of Australia to legislate on:

"Trade" and "commerce" have been broadly construed. The early case of W & A McArthur Ltd v Queensland declared:

"Trade and commerce" between different countries—we leave out for the present the word "intercourse"—has never been confined to the mere act of transportation of merchandise over the frontier. That the words include that act is, of course, a truism. But that they go far beyond it is a fact quite as undoubted. All the commercial arrangements of which transportation is the direct and necessary result form part of "trade and commerce." The mutual communings, the negotiations, verbal and by correspondence, the bargain, the transport and the delivery are all, but not exclusively, parts of that class of relations between mankind which the world calls "trade and commerce."

"Trade and commerce" has been subsequently held to include:

However, the High Court has also ruled that a distinction must be maintained between interstate trade and trade that is strictly within a State. In Wragg v New South Wales, Dixon J. remarked:

The distinction which is drawn between inter-State trade and the domestic trade of a State for the purpose of the power conferred upon the Parliament by s. 51 (i.) to make laws with respect to trade and commerce with other countries and among the States may well be considered artificial and unsuitable to modern times. But it is a distinction adopted by the Constitution and it must be observed however much inter-dependence may now exist between the two divisions of trade and commerce which the Constitution thus distinguishes. A legislative power, however, with respect to any subject matter contains within itself authority over whatever is incidental to the subject matter of the power and enables the legislature to include within laws made in pursuance of the power provisions which can only be justified as ancillary or incidental. But even in the application of this principle to the grant of legislative power made by s. 51 (i.) the distinction which the Constitution makes between the two branches of trade and commerce must be maintained. Its existence makes impossible any operation of the incidental power which would obliterate the distinction.

But the distinction between interstate and intrastate activity is not absolute. In Airlines of New South Wales Pty Ltd v New South Wales (No 2), Menzies J. noted:

If control of intra-State trade is necessary to make effectual the exercise of Commonwealth power, that control may be exercised by the Commonwealth itself regardless of the control exercised by a State and regardless, too, of the fact that at some previous time the Commonwealth, because of the control exercised by a State over its intra-State trade, refrained from the full exercise of its own power. Arguments based upon the extent of State legislative power, or, the extent to which that power has been exercised, to measure or confine the legislative power of the Commonwealth, must, since the Engineers Case, fall upon deaf ears.

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