You've named this one spot. But is that "numerous publicly owned lands" ? Ok, sure: There are some types of federal/national administered lands that perhaps there's some true rule. Like at National parks . Not sure of the exact status of your particular lake-shore (national park or ... whatever?). But other forms of federal land (blm and lots of NFS) are not dis-allowed. And you have oodles of other forms of public land in your area, that isn't of that type. Ie.: various types state, county, city lands, and perhaps types of fed. land where there isn't such strictures.
As for the logic you cite about the stones you can't pick up, well ... you gotta put yourself in their shoes: If they say "yes you can pick up stones" (afterall, they're just gonna get worn down to nothing anyhow), then : What's to stop someone from backing their truck up to the lake-shore and harvesting them for commercial sale on large-scale basis ? So ALL parks, beaches, forests, etc... (no matter WHO administers them), will have verbage that disallows harvesting, collecting, removing, etc... Right ? Lest the "camel's nose be in the tent", blah blah.
I bet such rules, when followed to their logical extreme, would technically disallow your 9 yr. old daughter from picking up a seashell at the beach here in CA, to use on her grade school art project. And if you asked enough of the powers-that-be: "Can I Pick up a seashell?", they'd probably have to say "no". But seriously now, did anyone really care ?
Not saying to throw caution to the wind, or traipse yourself in front of archie busy- bodies looking for trouble. But ... just saying don't over-think it. There's lots of places to md. I've heard of people md'ing the shores of the great lakes there. Not sure if there's certain beaches that are ok, versus others that aren't ? Or perhaps they didn't ask long enough and hard enough of enough people ? I dunno.
