i saw a good description recently where it said that BS7671 is directly referenced in other legislation which I haven’t seen before and it better explains my point. Therefore to prosecute, enforcement authorities need to use the actual “other” legislation which directly references BS7671. It is a good point because the additional health guidance isn’t referenced like BS7671.I haven't claimed BS7671 to be a statutory instrument, but simply pointed out that it is regulatory as you had incorrectly claimed otherwise.
The terms 'regulation', 'legislation' and 'statutory' are not interchangeable.