Pretty sure they've already used them in this country, we were shown loads of footage of riot control when I went to watch the police public order training.
(no mention of it there but there was an officer in one of the vids marking people so they could pick them up later)
As long as they're reasonably close enough to get some accuracy, should be safe, ish, ish....But they'll be in the deep sh!t if someone's eye gets shot.
Id rather have paint shot at me than rubber bullets, which have killed people, and broken bones...
(rubber bullets are slightly different in that they're meant to be shot at the ground infront of the rioter & then ricochet up into their shins or legs. They've killed mostly when they've ricoche'd too high or been shot direcly into the chest/stomach or head.)
edit: Meh, did some research, they don't use rubber bullets anymore (now acrylic), & there've been no deaths since 1989.