Some friends had a problem with the local kids damaging the flat roof on their garage, so they went out to take pics of the youths involved as evidence - then got a call from the police that the kids parents where making a complaint for taking pictures of the youngsters. Where the hell is the justice in that?

You can counter sue as you have evidence of there kids commiting a crime. Let them try it as the judge will soon look back at them like a dog at a new dish. Also alert the media what the police have said to you and record all incoming calls from them to protect you using modem spy a nice nifty prog. Make sure you inform them the calls are being recorded.
You can get a 56k modem to do it for about £10