Well a sin in not necessary illegal et vice versa .. I've always taken it as being based on the "do unto others as you would have them do unto you" sort of rule.
But.... if by parking on a yellow line you inconvenience someone else, in a manner that you would not wish to be inconvenienced yourself, is it not then sin.
<hr width=100% size=1>Think I'll draw some little rabbits on my head, from a distance they might be mistaken for hairs.