One in particular (UK Cycling Events) used to insist on helmet specifications that banned all helmets on sale in the UK!
They insisted on Snell or ANSI standards, both of which an EN 1078 helmet would fail
Once this was pointed out (multiple times) it was changed.They now have added EN1078, but still display a stunning level of ignorance by insisting on ANSI.
You must wear a safety-approved cycling helmet complying with latest EN1078, ANSI Z90/4 or SNELL standards during your participation in the event
ANSI was a US standard that was decided by a committee that hasn't been in existence since 1995, and in 1995 the ANSI Z90/4 was repealed and replaced with the ASTM - yep they are actually insisting on a standard that hasn't existed for over 12 years!
I would love to turn up in one of these:
Simply on th grounds that more modern helmets didn't fit the ANSI standard they required