When former president Clinton was being charged in the USA, the American legislators had to look at the meaning of out of date phrases and English Common Law from several hundred years earlier because phrases such as "High Crimes and Misdemeanours" and other early Common Law concepts were built into the current American Constitution. The USA were of course in charge of their own constitution and had taken over governing the country in the same way that the ECF took over the BCF but with a little more skill. Thats a decent analogy.
Sean Hewitt wrote: Well, I'll let others judge ...................that if something is referenced to then it must exist.
Provided the concept exists at the time of referencing it must continue for the currency of the document that makes the reference even though the reference would be more sensibly changed to FIDE rules.