I think that code of practice came out 12-18 months ago.
The problem is, that it is a code of practice, not law, and some forces choose to ignore it. Certainly, if a case gets to court it's worthless.
Personally, I don't have a problem with it. If folk choose race cans and tiny number plates, thay have to accept the consequences. Further, hopefully they'll attract plod's attention while I go quietly on my way.