1. The AMA has no 'juristiction' over local flyers. Only if they are AMA members and make a claim against the AMA insurance can the AMA become involved.
2. A letter from the club via a lawyer to the landowner (NOT the rogue fliers) could have your desired result.
3. The easiest solution and most in keeping with the spirit of model aircraft being a fun hobby, is to approach the rogue fliers and set up a frequency sharing plan. Set aside their used freqs and mark them unuseable at your club. They have as much right to fly and use the freq at their location as you have at yours.

Fritz