Like David Dong stated.
However, regardless of the local laws, the person is still restricting or blocking access to private property. If you happen to know which house they're visiting, go over and ask nicely first (being polite usually gets far better results the first time). If you don't know where they're visiting or they give that "I'll be out in a few hours" bull, then call the cops and get him/her towed.
Of course, putting a battering ram on your vehicle and just pushing them out of the way is very effective if you don't mind the legal ramifications or the possibility of retribution being meted on your property.
Good luck fedge.