I'm not familiar with the law very well though and I'm betting a lawyer would have picked up on this video by now if the cop exceded his authority.
Still, great shomen ate! Looked almost like Shodokan kata to me
I suppose that every community decides for itself the amount of violence it's law-keepers are allowed to employ. I have the good fortune of not living in that one.
As to the technique, it is applied to unresisting and unskilled person, so yeah it works, so what? Imagine this was a dojo and you are witnessing a yudansha smashing a first time student into the mat.