CITATION: Canada Post Corporation v. Hamilton (City), 2016 ONCA 767:
 The following section first articulates the general principles of the division of powers analysis, specifically the doctrines of ultra vires and paramountcy, and then applies them to the facts of this appeal.
(1) The general principles
(a) Pith and Substance
 The first step in a division of powers analysis is to characterize the law being challenged. This characterization is a matter of determining the "pith and substance" of the challenged law: Union Colliery Co. of British Columbia v. Bryden,  A.C. 580 (P.C.), at p. 587. In more contemporary language, this step has been described as determining the "true character" (RJR-MacDonald Inc. v. Canada (Attorney General),  3 S.C.R. 199, at para. 29) or "true nature of the law" (Canadian Western Bank v. Alberta, 2007 SCC 22,  2 S.C.R. 3, at para. 26) or of "identifying the 'matter' to which [the law] essentially relates" (Canadian Western Bank, at para. 26).
 Although the terminology is well-settled, there is no single test for determining a law's matter and, as the Supreme Court cautioned in R v. Morgentaler,  3 S.C.R. 463, at p. 481, "[t]he approach must be flexible and a technical, formalistic approach is to be avoided."
 The initial question of "what is a law's pith and substance" invites two prior questions: "[w]hat in fact does the law do and why?": Quebec (Attorney General) v. Canadian Owners and Pilots Association, 2010 SCC 39,  2 S.C.R. 536, at para. 17 ("COPA"), citing D. W. Mundell, "Tests for Validity of Legislation under the British North America Act: A Reply to Professor Laskin" (1955), 33 Can. Bar Rev. 915, at p. 928;see also Grégoire Webber, "Asking Why in the Study of Human Affairs", (2015) 60:1 Am. J. Juris. 51 at p. 54. These two paths of inquiry are often expressed as a search for: (1) "the purpose of the enacting body", and (2) "the legal effect of the law": Canadian Western Bank, at para. 27; Reference re Firearms Act (Can.), 2000 SCC 31,  1 S.C.R. 783, at para. 16. These two inquiries are related: while purpose is often "the key to constitutional validity", "[l]egal effect is often a good indicator of the purpose of the legislation": Morgentaler, at pp. 482-83.
(i) Effect of the law
 The effect of the law can include both (1) legal effect, and (2) the practical consequences that result from legislation: Morgentaler, at pp. 482-83; Quebec (Attorney General) v. Lacombe, 2010 SCC 38,  2 S.C.R. 453, at para. 20.
 Acts of legislation are, paradigmatically, reasoned plans enacted either to change or confirm existing legal rights and obligations of persons. Thus, the legal effect of legislation is determined "from the terms of the legislation itself", by asking how the legislation affects the legal rights and obligations of those subject to it (Morgentaler at p. 480. See also, Richard Ekins, The Nature of Legislative Intent (Oxford: Oxford University Press, 2012), at pp. 121-27).
 The effects of legislation are an important indicator of its purpose. The Supreme Court has cautioned, however, that the enquiry into effects not be truncated by considering only the means chosen by the legislature and ignoring the more ultimate ends. For example, in Ward v. Canada (Attorney General), 2002 SCC 17,  1 S.C.R. 569, a federal regulation prohibited the sale of two types of young seals. The Supreme Court rejected the argument that the subject matter of the legislation was the regulation of the sale of seal products, which would be a matter within provincial jurisdiction (i.e., as a matter related to "property and civil rights in the province"). The immediate effect of the regulation was to prohibit the sale of seals. But this effect was only an intermediate end: a means, by way of removing the financial incentive to hunt seals and curtailing the commercial hunt, to achieve the more ultimate end of protecting a fisheries resource. An adequate account attends to both the intended effects and means chosen to bring them about.
(ii) Purpose of the enacting body
 The effects of legislation are one guide to its purpose, but there are others, bearing in mind that the relevant purpose for analysis is, as Binnie J. stated at para. 27 of Canadian Western Bank, the purpose of the "enacting body" in enacting the legislation, and not the purpose of any individual member.
 In determining the purpose of the enacting body, a reviewing court may consider both intrinsic evidence (evidence contained within the text, such as statements in a preamble or a purpose clause) and extrinsic evidence (evidence outside of the text, such as minutes of parliamentary debates): Canadian Western Bank, at para. 27.
 This analysis is not concerned with the motives of the government in proposing the legislation, or the motives of the enacting body or of any of its individual members: Quebec (Attorney General) v. Canada (Attorney General), 2015 SCC 14,  1 S.C.R. 693, at paras. 35-38 ("Gun Registry II"). Motive, in this context, should be understood as the desire to achieve some end other than the immediate change in legal rights and obligations achieved by the legislation.
 For example, in Gun Registry II, the Supreme Court considered Quebec's argument that federal legislation resulting in the destruction of a firearms database was motivated by a desire to prevent or hinder Quebec from developing its own long-gun registry. The court decided that although that may well have been the government's motive, it did not play a role in the characterization of the matter of the legislation. At para. 38, the court commented:
Quebec's submissions, in our respectful view, confuse the subject matter of s. 29 of the ELRA with Canada's motives and the means employed by Parliament. In determining the true character of s. 29, we are not concerned with whether destroying the data is good policy, whether Canada's motives were sound, or whether the destruction of that data conflicts with the policy objectives of Quebec. We recognize that the federal government's ultimate goal may well have been to prevent Quebec from creating its own long-gun registry. We also accept that the destruction of the data is the means chosen by Canada because of its irremediable nature. That being said, these considerations are not indicative of a "colourable" purpose from a division of powers' perspective. An intention on the part of one level of government to prevent another from realizing a policy objective it disagrees with does not, on its own, lead to the conclusion that there is an encroachment on the other level of government's sphere of exclusive jurisdiction.
The subject matter of legislation is thus distinct from the motives of government and of individuals within a government.
(b) Heads of power
 Once the matter of the challenged legislation is ascertained, the next step is to determine whether the matter comes within one of the heads of power allocated to the enacting legislative body by s. 91 or s. 92 of the Constitution Act, 1867. If not, the legislation is ultra vires and void.
 Legislation will not be ultra vires, however, simply because its subject matter, for another purpose, could have fallen under the jurisdiction of the other level of government under a different head of power. The double aspect doctrine provides that "subjects which in one aspect and for one purpose fall within sect. 92, may in another aspect and for another purpose fall within sect. 91": Hodge v. The Queen (1883), 9 A.C. 117, at p. 130 (P.C.). Accordingly, the doctrine contemplates that some subjects will fall equally under two distinct heads of power, one federal and one provincial: Rogers Communications Inc. v. Châteauguay (City), 2016 SCC 23, 397 D.L.R. (4th) 611, at para. 50.
 This double aspect raises the possibility of conflict between valid federal and provincial laws that both deal with the same subject matter. The doctrine of paramountcy stipulates that such conflict is to be resolved in favour of federal legislation: Canadian Western Bank, at para. 32. Where there is a conflict, federal legislation is paramount and the conflicting provincial legislation is inoperative to the extent of the conflict.
 The Supreme Court has recently clarified its jurisprudence on what is required for a conflict: Alberta (Attorney General) v. Moloney, 2015 SCC 51,  3 S.C.R. 327, at paras. 17-29. It summarized when a conflict will occur, at para. 29:
[I]f the operation of the provincial law has the effect of making it impossible to comply with the federal law, or if it is technically possible to comply with both laws, but the operation of the provincial law still has the effect of frustrating Parliament's purpose, there is a conflict.
Of the Law Societies of Upper Canada and Nunavut