I can't say this question was well-researched [answers could easily be obtained using Wikipedia], however the closing reason stating that it belongs to DIY.SE seems to be simply because it's asking about [the existence of] NEC-like regulations [in the UK in this question]. This makes me uneasy, as a precedent.
Sure there's some overlap with DIY.SE on that topic. I'm inclined to mark for migration to DIY.SE questions in which the OP can't wire a couple of things together without help, and in that respect I think I can draw an analogy with Unix.SE vs Ubuntu.SE. But this question was rather general; the OP didn't ask for any help with some specific home installation. Futhermore after looking at what CEI does, that's like also sending questions about IEEE standards and FCC regulations to DIY.SE! (And on a related note, cross-over questions have remained in the realm of feature request on SE insofar...)
Reopening that question wouldn't serve any purpose in terms of new answers, and I think the existing ones are sufficient, so I'm not going to nominate it for reopening, but I'd like to hear more detailed opinions on the issue of questions about regulations. Are they really off-topic here?