This is both a civil and a criminal matter. They are destroying your property and therefore could be charged by the police. Unfortunately the police don't like getting involved in anything like this and are unlikely to take any action unless you complain to a higher officer. As far as the civil law is concerned you can obtain a court order for interdict which is an order to stop them doing what they are doing. If they disobey the order they will be in contempt of court and can be fined or in extreme cases imprisoned. You can also sue for damages being the cost of replacing the trees or loss of amenity. To run a civil case you will need to instruct a solicitor but you should claim the expenses of any court action from them as well as the other orders mentioned above. I hope that helps. Please leave a positive rating so that I am credited for my time.