ORIGINAL: Robotech
There's your solution. If the guys are not AMA members and are flying on public land with no coverage for the county then the "guy from the county" has exposed the county (that's you too, the taxpayer) to all sorts of liabilities. Give him another shot at getting them off county property. If he fails, go to his superiors or go pulblic.
That's a great solution. Support model aviation for everyone that complies with your dictates of how it should be done. Jimmy Hoffa would have loved it.
Abel