Serve and protect?

As a lad, I never played hopscotch, but I understood the principles, including that you needed to map out a grid on the pavement, usually with chalk, to indicate where you needed to step to stay in the game.  It's been played since forever, but a girl in Kent has now been warned by the police that drawing out a hopscotch grid on the pavement - in chalk - could amount to criminal damage. Where on earth do they get these idiots??