And the possibilities beget possibilities. Your trespassers being able to park on your lawn as they apparently do says to me that your street does not have curbs; basically where the street ends is where the lawn begins. So, you being a good neighbour and all, and concerned about possible drainage issues on your property due to poor water management, rent a small backhoe like the one by Kioti or cat or ?? and decide to practice with it by digging a ditch along the frontage of your property. if it is inside the property line and there are no buried or hidden encroachments like gas lines or water/sewer services then you shouldn't even need a permit; you are just practicing after all, but it might be safer to check first, jic. Check with the neighbors, maybe they have water issues too and would be interested in sharing the rental fee so you can practice more.
And then you dig your ditch as close to the road as possible. Make it oh, 2-3 feet deep, no deeper and be sure to bevel the edges to make it look professional. Lay in a little grass to finish it off and Hey, Presto!! Anyone trying to park on the lawn ends up in the ditch. It's all on them for trying to put their vehicle somewhere it weren't supposed to be. They get to pay the cost of having it towed out; OR, followup with the suggestion above and once you have a few cars trapped, bring out the blow up wavy dude and the used cars for sale signs and if someone happens to protest, well they had to trespass the property just to fall into the ditch. And surprise, surprise, what license plates?? Confiscation laws in the county, maybe???
(I really have way too much time on my hands when I start to generate sh*t like this)
Nick