How do your get a car you own off of someones property if they wont let you on the property?

If you can prove it's yours (title, payment book, registration is in your name, etc) then the police or constable are often willing to go to the property with you to keep the peace, while you load up/start up your vehicle and leave. If that's not an option, but you can prove it's yours, then hire a repo man, (look for "Asset Recovery") or ask a beater car lot or small bank who they use for repo's. Expect to pay somewhere around $300 for the repo, and be prepared for some minor damage.