R v. Nolan said:
[19] On the level of principle, it is important to remember that the definition of "peace officer" in s. 2 of the Criminal Code is not designed to create a police force. It simply provides that certain persons who derive their authority from other sources will be treated as "peace officers" as well, enabling them to enforce the Criminal Code within the scope of their pre‑existing authority, and to benefit from certain protections granted only to "peace officers". Any broader reading of s. 2 could lead to considerable constitutional difficulties. Section 92(14) of the Constitution Act, 1867 provides that the administration of justice falls within provincial legislative competence. See Di Iorio v. Warden of the Montreal Jail, 1976 CanLII 1 (SCC), [1978] 1 S.C.R. 152, and Attorney General of Quebec and Keable v. Attorney General of Canada, 1978 CanLII 23 (SCC), [1979] 1 S.C.R. 218. Although the ability of the federal Parliament to create a national police force has never been challenged and any such exercise of authority is presumptively valid, to treat s. 2 of the Criminal Code as a broad grant of authority to thousands of persons to act as "peace officers" in any circumstances could well prompt a constitutional challenge. In the context of division of powers, legislation should be interpreted, when possible, so that it is not ultra vires. The assessment of legislation under the Canadian Charter of Rights and Freedoms is, of course, subject to different considerations. See Manitoba (Attorney General) v. Metropolitan Stores Ltd., 1987 CanLII 79 (SCC), [1987] 1 S.C.R. 110.
[20] I would therefore conclude that the definition of "peace officer" in s. 2 of the Criminal Code serves only to grant additional powers to enforce the criminal law to persons who must otherwise operate within the limits of their statutory or common law sources of authority.
R. v. Nolan, [1987] 1 SCR 1212