Opinion of the Court
Service, all of those provisions show that “ANILCA preserves [its] authority to regulate conduct on navigable waters” in national parks. Brief for Respondents 42.
But ANILCA does not readily allow the decoupling of navigable waters from other non-federally owned areas in Alaskan national parks for regulatory (or, indeed, any other) purposes. Section 103(c), as we have described, speaks of “lands (as such term is defined in th[e] Act).” 16 U. S. C. §3103(c); see supra, at 9. The Act, in turn, defines “land” to mean “lands, waters, and interests therein.” §3102(1)–(3); see supra, at 9. So according to an express definition, when ANILCA refers to “lands,” it means waters (including navigable waters) as well. And that kind of definition is “virtually conclusive.” A. Scalia & B. Garner, Reading Law: The Interpretation of Legal Texts 228 (2012); see ibid. (“It is very rare that a defined meaning can be replaced” or altered). Save for some exceptional reason, we must read ANILCA as treating identically solid ground and flowing water. So if the Park Service were right that it could regulate the Nation River under its ordinary authorities, then it also could regulate the private fields and farms in the surrounding park. And more to the point, once Section 103(c) is understood to preclude the regulation of those landed properties, then the same result follows—“virtually conclusive[ly]”—for the river.
And nothing in the few aquatic provisions to which the Park Service points can flip that strong presumption, for none conflicts with reading Section 103(c)’s regulatory exemption to cover non-federal waters. The most substantive of those provisions, as just noted, contemplate some role for the Service in regulating motorboating and fishing. But contra the Park Service, those sections have effect under our interpretation because both activities can occur on federally owned (and thus fully regulable) non-
103(c) and Title VI.
