>> Adhere the label to the side window or windshield. Once stuck onto a window, the warning requires scrapping or a razor blade to remove.

Vandalism, basically.

Those stickers should be illegal. It's pettiness at its worst.

Edit: illegal to use on people's cars/property that is.

One of my very first deployments was to Germany, where we guarded a hospital. People like the colonel's wife would park in the ER drivethrough for up to an hour at a time. Yes, blocking emergency access for any ambulance that might need to come through. I got very butthurt about this and the old sargeant of the guard on duty smiled real big and opened up the bottom drawer of his desk, dug way back in there, and extracted a stack of 8.5x11", bright neon orange, "impossible to remove without fucking up the car window" stickers that said nasty things about parking like an asshole (in German and English). They were very aggressive stickers. But imagine my delight when he told me to stick them on the cars parking in the ER drivethrough. My only rule was that I couldn't put them over the driver's side windshield and block their vision forward. So I started slapping these fat motherfuckers on the driver's side window. Adults wept and threw tantrums when they saw these stickers. The kind of reaction you would expect out of someone that parks where the ambulance needs to go at a hospital when bringing in someone that might be dying.

There are times when these stickers are used for the forces of good, you know.

Edit: I still have about half of that stack of stickers at home. I still only ever use them for the forces of good. :)

"Fluorescent label material gets your attention 75% faster than standard stickers."

I wonder if they were double-blind tests.

A hard-to-remove sticker on the windshield for parking in the wrong place? Won't that guarantee that the car will be staying in that wrong place for a lot longer? It doesn't sound safe to drive with a sticker in the middle of your windscreen.

This is just plain destructive and counterproductive. Use something that's easily noticed but also easily removed.