It comes off easily, because the tint vinyl(?) is easy to take off, even with just fingers. Just something sharp to get the vinyl running, and it comes off nice and easy, mostly even without any glue left on the window. And yes, because your car is not legal to run on the street , you have to decide, whether to leave it there (doh!), or scrape it off and drive away. They can fine you , but mostly our police officers are sensible on this matter , and they just ask you to take it off , or else you can't drive anywhere from the scene.
Edit : Oh and that applies for all types of tints I guess , because I got a 5 year warranty on the job, and 20 years (!!!!!!) on the tint vinyl. Its just fits so easily and it is easy to take off, and so far I cant see any defects on any of my cars. I remember an incident on the evening news , where they made an E39 M5 driver scrape it off , and he got both tints of in 5 minutes or so, ran the glass up , like it was never there.