The lot is mine; the car is yours. You can put whatever you want in your car, including a harem of fuzzy llamas, and I can tell you whether or not your car is allowed in my lot.
I have a right to fence in my lot, and you have no right to plow through the fence, or to run through the guardpost. If I don't put up a fence or guardpost, the property is still mine and not yours. For society to work properly, most people need to realize that.
Period. End of story.