From http://www.ukpsf.com/paintballandthelaw.htm
To stay within the law a paintball marker must not be fired above 330fps when using an average weight paintball, this equates to 12 ft/lbs. All tournament markers are restricted to a maximum velocity of 300fps, which equates to 9.9ft/lbs and site markers should be used at between 250-280fps to be safe for customers. This equates to 7ft/lbs-8.7ft/lbs.
Paintball markers must not be fully automatic i.e. when pulling the trigger once, two or more paintballs must not be discharged.