There are already laws to cover this but the police won't act.
Simple trespass is a civil offence. But aggravated trespass is a criminal offence. So if someone enters someone else's land and causes any damage whatsoever, even for example scratching a gatepost, or prevents the owner of the land doing something on his land that he is entitled to do, then the police can act. But they won't because they don't want to get involved, haven't got the manpower, couldn't give a stuff or some other excuse.
So making any more laws in connection with this will have exactly the same result, ie the police conveniently looking the other way. The only circumstances under which you would be likely to get any meaningful action is if some undesireables actually camped on some land belonging to the chief constable. Then you would see just how effective our existing laws actually are.