Shoot them down.
The MQ-1 Predator has a $4 million price tag, and prices seem to go up from there.
I bet there are effective homebrew anti-aircraft solutions that can be put together for a few hundred dollars. Maybe even less. Maybe cheaply enough to make them effectively disposable.
Let a local law enforcement agency get a few million dollars worth of the things turned into smoking heaps of scrap metal, and spend more time and money investigating that than they would have saved using them, and see how keen they are on keeping it up.
I think it's eminently doable.