nicnavina, on 02 May 2012 - 03:33 PM, said:
How do I report a geocache that has been placed on private property without permission? There is a "NO TRESPASSING" sign not ten feet from my most recently found geocache (see picture below) and my boyfriend and I didn't see it. We got in trouble for trespassing when we were signing the log book. The landowner threatened to call the police. I don't want anyone else to get in trouble or have the police called on them because they didn't see the sign.

The most immediate reponse would be to post a "Needs Archiving" log, explaining your experience. The reviewer will be notifed and he/she will probably archive the site.
Less direct would to be to contact the cache owner and advise them that the site is on private property. They might not know. This approach might ruffle fewer feathers but if there is the threat of police I would favour the former approach. We don't want the boys in blue getting to have a bad opinion of geocaching.