Q. On Shabbos police chalked my car tire so that they could come back later and ticket me for parking for more than three hours. Is there permissible way for me to clean off the chalk?
A. Horav Shlomo Miller's Shlit'a opinion is that if the marking does not constitute any letter or expressive sign but just a plain simple line mark on a tire, one can make it somewhat wet and then clean it off and remove with a (pre-cut) paper towel or similar, as one would clean a plastic tablecloth.
There may be no issue of violating any dina demalchusa or a government law, since they may not even legally place a mark on your car. (See Los Angeles Times (Aug 02, 1989): Woman Not Guilty of Wiping Off Chalk Mark to Avoid Parking Ticket. However, by-laws do change from location to location)
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit'a