Well of course you CAN (I may or may not, myself). But MAY we, if it please The Crown? It would never have occurred to me to wonder, having wandered out the door of my LGS with one many years ago and not thinking twice about it since.
I have an unissued Yugo in the safe. Delivered to my door on c$r license. Has to be fixed mag. Making it into detached makes the bayonet and grenade launcher switch more killy.