Within the UK certainly NOT allowed.....the arguement "could" be used in relation to and against Angel LCD's but as they are locked out by a software command not a physical switch so then they are ok to be sold in the UK. All other mode capable markers are not legal for sale...Shockers Turbo's are ok due to the "grey" area that Turbo finds itself in (of course Turbo is banned within tournys but that is a self regulating ban, not an official legal one) If you are talking about an electro framed marker like the Centerflag uprising or their type then unless the modes are software locked and flicking of the internal switches does nothing then you cannot legally own one of these in the UK...Centerflag will sell you a UK version of their grip btw as their normal version is full mode capable, the other makes such as E-99 etc are capable of the modes by moving of the switches in the grip so in that form they are not legal in the UK...it is the movement and addition of switches that is the important issue here.
So to round up.
no switches = legal,
switches present but disabled in the software = legal,
switches in place and useable = illegal.
Edit (damn you Baca I was re-typing my reply to ensure it read properly and in you popped
)