In the UK the building regs are merely 'approved documents'intended only as guidelines and in themselves have no legally-enforcable standing. As such they are supposed to be subject to interpretation (as in the case of listed buildings with PPG15).
But, most BCOs are inadequately-trained and have little experience of anything other than bog-standard building techniques, and thus will often refuse to negotation on interpretation.
Things became far worse last April with the new, post-Kyoto, approved docs, including Part L, which deals with insulation. Even the government now admits that the regs are now absurdly complex - and have commissioned a 'think tank' to come with with secondary documents and interpretation guides.
That is a long way off, however, and until then the building industry will remain subject the the caprice of the BCOs. Some of them are good, mut many of them are a***holes. After all, anyone with the nous chooses to become a surveyor or a structural engineer rather than work in an understaffed and overworked environment.
The US situation is different, and I mean no offences to US building inspectors.