That should absolutely still be on the books. You'd have people cleaning fish in bathrooms.
That should absolutely still be on the books. You'd have people cleaning fish in bathrooms.
https://www.law.cornell.edu/cfr/text/36/261.16
"The following are prohibited: (c) Cleaning or washing any personal property, fish, animal, or food, or bathing or washing at a hydrant or water faucet not provided for that purpose."
This is the sort of thing that would just be a normal rule, in a contract or something, in a privately-managed park. For a federal park, it's perfectly reasonable for it to just be a federal law.
You could also imagine a world where it's simply illegal to be in a federal park without signing a contract with the government, which would get these sorts of things out of the CFR, but that seems like it would be worse for the American people at zero benefit. And personally, I'd still call things in those contracts "federal regulations".
You could also imagine a world where national parks become privatized.
The issue here is that the statute authorizing criminal penalties covers a whole range of national park regulations, some of which clearly merit stiff penalties, and some of which are just about washing fish safely.
So to forbid washing fish at a faucet in a national park... you literally do have to make a federal law (or a regulation with the force of federal law).
This is also why they have their own law-enforcement agency (the United States Park Police): Congress was, for a very long time, reluctant to authorize a general federal police force, so many agencies have their own specific police force operating solely within that agency's jurisdiction. It also creates fun inter-jurisdictional issues since the U.S Capitol building has its own separate police force, but the Capitol building is on the National Mall, which is Park Police territory.