Interesting thread. I've detected library lawns w/o issue before.
"Won't hurt to ask" ? Well if they say "no" (when perhaps no such rule exists), then to me, that "hurts". Because they might have images of geeks with shovels, and simply pass out the "safe" answer (when in fact might never have given the matter a moment's thought). To me, that "hurts"
Do you have any examples of anyone being arrested, jailed, cuffed, ticketed, for md'ing a library lawn ? (just curious)
Technically yes, this is true. But the moment you go down THAT path, is the moment you can just give up detecting on every speck of public land. Because the same can be said of everywhere. I mean .... when someone gets into this hobby of metal detecting, it seems to me that it might have occurred to them that it involves "taking things" that "belong to the taxpayers". If that's wrong (which, yes, a lawyer could probably argue), then that's the day you and I have chosen the wrong hobby. It's intrinsic in the definition of our hobby from the git-go.
I realize you're only exaggerating to make a point, but .... the example you give (of digging holes in the freeway) is a distinct example of inherent evil, wrong, damage, etc.... If that's the definition of md'ing, then everything else you're saying logically follows. But since when is md'ing inherently evil and damaging ?? If someone is leaving THAT degree of damage, then they need to repeat target retrieval 101 class.
Sure. And they can do that by looking up said rules for themselves. Right ? And if no rule exists that says "no metal detecting", then presto, it's not disallowed. Right ? And to the extent that "rules might change", fine then: So too does the rule books. If a rule is updated, then presto, it's in the updated rule list that are available for public viewing. No need to go asking bored pencil pushers and risking a "safe" answer.
Perhaps. Sure. And I consider metal detecting to be a proper & legitimate "use" of the facility. Don't you ?
Missed you too 
Yeah, I got too sarcastic in mimicking someone's point, that it was deemed ridicule. So I got a time-out
As for this type question: There's always a middle-ground. So I guess it takes both extremes (the brazen to the timid) chiming in, to illustrate the pros & con's. To find the right middle ground.
Good to be back. Just got a few seated dimes @ a ghost town trip, so I've been busy none-the-less
. Been trying to carry your water, but, glad to have you back to carry your own load. 
