I always thought that you could own an RIF without a defence, but you just couldn't buy one. So for example before I was 18 my dad would use his UKARA to get me a gun, so it'd be my property but because it was a gift it was legal to own without a defence.
I also thought that the UKARA was to protect retailers rather than players however i'm more than happy to be corrected because I'm not well read up on them and I've never really bothered with them, mostly because I'd just buy guns from the Republic of Ireland and I've never had any hassle bringing them back across the border or having them shipped directly.