It should be noted that the majority but by
no means all guns powered by carbon dioxide
which discharge paint pellets and which are
used in adventure games are unlikely to cause
serious injury, nor were they designed as
“weapons”. As such, they should not be
considered to be “firearms”.
Taken from Home Office Guidelines regarding Firearms, 2002, page 7.
Naturally, this could be amended, i dont have access to teh current PDF, though I was lead to believe this was teh current guidelines...if anyone has an updated link, please let me know.