i have been told that they are technically illegal in the uk also (someone at UKPSF), might be a grey area in the law. i was told that a paintball gun stops becoming a paintball gun when you fire things other than paintballs through them. i think the grey area concerns what the marker is classed as when firing things other than paintballs. 'apparently for it to be legal it would have to be set at 50fps', which is fook all.
i do not know if this info is correct, nor is it my opinion, just what i got told one day. if it helps it helps.