In accepting the honour of writing an article for The Cambridge Law Journal, and in deciding to review some aspects of Canadian constitutional law, I realize that I must assume a good deal of knowledge on the part of my readers, otherwise it would be difficult to know where to begin, where to end, what to say, what to omit. For my immediate purposes it will be sufficient to point out that Canada is a federation of nine provinces created under the British North America Act, 1867, carrying on its executive, legislative, administrative and judicial activities in public and private law under that Act and its amendments and under the great landmarks of English constitutional law in so far as not modified or changed by validly enacted federal or provincial legislation. Legislative powers are divided between the federal and provincial legislatures in such a way as to exhaust the whole field, which is not fenced, as in the constitutional law of the United States, with any constitutional limitations. Granted the legislative power, the manner of its exercise cannot be questioned in the Courts by any arguments drawn from a Bill of Rights, or by the many refinements, moral, political or legal, which flow from ‘the privileges and immunities’ or ‘due process’ clauses of the American constitution. In Canada the doctrine of legislative supremacy prevails. Canadian legislative powers are distributed under the creating Act of 1867. To the provincial legislatures belong certain exclusive enumerated powers under section 92, while, under section 91, the undefined residue belongs to the parliament of the Dominion. For the moment detail is unnecessary. I purpose to view (a) the immediate historical evolution of these legislative powers in order to appreciate (b) the judicial process in relation to them. I shall not concern myself with the minutice of this process, fascinating as they are, but confine myself to certain aspects of it which have become fundamental. I shall conclude (c) with a short view of the treaty-making power, as already it is under further discussion in Canada in the hope of peace ahead. I have specially selected these points of view for a law journal, because federalism and federal law and the judicial process in relation to them are matters of perennial interest and are already in prominence in connexion with the proposed reconstructions of the world. In addition, the judicial process in relation to the British North America Act, 1867, provides an important chapter in the study of stautory interpretation—a subject of equal perennial interest. I refrain from adding anything of a comparative nature, for I have neither the space nor the qualifications to go beyond legal analysis and reach the economic and social life of other federations, without an expert knowledge of which comparative law is of little worth.