It is often prudent to set out in a statute the qualifications of and process for selecting members of administrative bodies. It would be prudent to do so with the Canadian Senate too, but doing so must take account of an important recent decision on constitutional amendment in Canada.
The leader of the Liberal Party of Canada, Mr. Trudeau, has proposed to make appointments based on recommendations from an advisory committee. The question is whether this is lawful in light of the Supreme Court of Canada's conclusion in Reference re Senate Reform, 2014 SCC 32 that non-binding elections to that august body could not be held without a constitutional amendment.
Part V of the Constitution Act, 1982, provides that changes to the "method of selecting Senators" require a constitutional amendment (s. 42(1)(b)). Consultative elections ran afoul of this in two ways, in form -- i.e. the text of the Constitution -- and substance -- i.e. the "architecture" of the Constitution ("the Constitution should not be viewed as a mere collection of discrete textual provisions. It has an architecture, a basic structure", para. 27).
Substantively, elections would change the character of the Senate:
 The proposed consultative elections would fundamentally modify the constitutional architecture we have just described and, by extension, would constitute an amendment to the Constitution. They would weaken the Senate’s role of sober second thought and would give it the democratic legitimacy to systematically block the House of Commons, contrary to its constitutional design.Formally, the Court held, the "broad wording" of Part V "covers the implementation of consultative elections" (para. 64). It was not enough that the Prime Minister retained ultimate appointment discretion, because the "plain meaning" of the text "goes beyond the formal mechanism of appointment" (para. 67):
 By employing this language, the framers of the Constitution Act, 1982 extended the constitutional protection provided by the general amending procedure to the entire process by which Senators are “selected”. The proposed consultative elections would produce lists of candidates, from which prime ministers would be expected to choose when making appointments to the Senate. The compilation of these lists through national or provincial and territorial elections and the Prime Minister’s consideration of them prior to making recommendations to the Governor General would form part of the “method of selecting Senators”... My emphasis.
How do Mr. Trudeau's measures stack up?
They pass the test of substance with flying colours. The Court noted that the Senate has two fundamental features, providing a "sober second thought" as to proposed legislation and "the additional role of providing a distinct form of representation for the regions that had joined Confederation and ceded a significant portion of their legislative powers to the new federal Parliament" (at para. 15), through which it came to serve "as a forum for ethnic, gender, religious, linguistic, and Aboriginal groups that did not always have a meaningful opportunity to present their views through the popular democratic process" (at para. 16). Striking a committee with a mandate to find non-partisan leaders in various fields of public policy, with a view to ensuring regional and minority representation, would surely enhance the fundamental features of the Senate.
The formal test presents difficulties, however. An advisory committee would surely form part of the "entire process" of appointment, informing the Prime Minister's "recommendations". Even if the committee only presented a shortlist, from which the Prime Minister would be free to make the ultimate choice, his discretion would be somewhat constrained. The committee's recommendations would shape the "entire process".
But it would be absurd to conclude that these difficulties doom Mr. Trudeau’s reform proposals. First, it allows form to triumph over substance in the case of a conflict between them. Consultative elections did not present any difficulties on this score: they violated both the form and substance of the Constitution. But must form slavishly be followed at the expense of substance? Second, it means that informal discussions that are not placed on a statutory footing are less likely to violate the Constitution. Yet this is to prefer decision-making in the dark to decision-making in the open (a phenomenon I have worried about before). Worse, it is to prefer decision-making in the dark by elites, as Dwight Newman has observed.
What should we do when form and substance clash? Consider this passage:
 The rules of constitutional interpretation require that constitutional documents be interpreted in a broad and purposive manner and placed in their proper linguistic, philosophic, and historical contexts...Generally, constitutional interpretation must be informed by the foundational principles of the Constitution, which include principles such as federalism, democracy, the protection of minorities, as well as constitutionalism and the rule of law...
 These rules and principles of interpretation have led this Court to conclude that the Constitution should be viewed as having an “internal architecture”, or “basic constitutional structure”...The notion of architecture expresses the principle that “[t]he individual elements of the Constitution are linked to the others, and must be interpreted by reference to the structure of the Constitution as a whole”...In other words, the Constitution must be interpreted with a view to discerning the structure of government that it seeks to implement. The assumptions that underlie the text and the manner in which the constitutional provisions are intended to interact with one another must inform our interpretation, understanding, and application of the text. Citations omitted, my emphasis.
This passage suggests that form and substance should not be considered as independent prongs on which problematic constitutional reforms are impaled. Rather, a more holistic analysis should be performed, with both form and substance (including the Constitution's foundational principles) relevant to whether a proposed reform requires a constitutional amendment.
A holistic analysis would approve of Mr. Trudeau's proposals, because they would further the fundamental features of the Senate, while also respecting the foundational principles of protection of minorities, federalism and democracy by ensuring that criteria are set out to appoint regionally and ethnically diverse Senators in a transparent process. It would be perverse to conclude that such a set of proposals could not be implemented without a constitutional amendment.