Share 'Impeding the flow of traffic'

Can someone explain how this law is enforced? I have never had a problem with it in the past. I was riding my bicycle predictably and as far to the right as I could, when suddenly I was buzzed by a van passing way to close. Whoa! Pass with 3 feet! I exclaimed. While not more then a second later over the PA from local law enforcement comes, "Why don't you get on the sidewalk before you get killed…