OK, I met with the county today, along with the other users of the area (trap club & dragstrip). I explained the risks to everybody if our planes start showering down out of control, possibly caused by the non-club flyers operating within 3 miles. Everybody hates the situation we're in, but the county doesn't think they can legally kick these guys out from the boat ramp area, as it is public property. They (county) emphasized they would really like to see these guys either (1)join the club and make use of the excellent site we have, or (2) do the common sense thing and fly somewhere outside 3 miles. Realistically, nobody thinks either of these things will happen. So the county encouraged the club to approach the rogues and make an attempt to work out a frequency sharing arrangement. Interestingly, during the conversation, the county guys' boss said "Hey, isn't this the same group of guys we ran off from site XYZ a couple years ago? That turned into a real brouhaha after neighbor complaints, and almost turned violent."
The county guy also said what he would really like to do is just tear the parking lot out at the boat ramp, as I guess there are some other activities taking place they would also like to stop; however the parking area was built as a part of another very specialized activity years ago, and the asphalt there is 16" thick!! The county doesn't have the kind of budget to deal with that kind of project.
I'm not surprised at the outcome, and I'm not optimistic about a frequency sharing agreement, but it is what it is. The whole situation is just going to be a thorn in everyone's side...but I suspect that eventually, and I'm talking years down the road, this situation will just go away. It could be from near complete upgrade to 2.4, or it could be to rogue attrition, but it will go away.
At least the club's cards are on the table, ans we have the support of our neighbors.

I'm considering this a dead issue.