"Region" as in US, rather than a particular part of the US?
Maybe some kind of import/export rule or law has changed?
It does sound funny though? I have never heard of having to prove age, to buy a "complete" knife, much less a kit (or blank core) The length of the blade might matter, in some places, though I think that is more about carrying in public, rather than at point of purchase.
Region in international terms, so no knives sold in the U.S., and mostly one can't see them unless one switches the website to some other regional setting (e.g., Canada).
>Yes, there are some goods that are no longer available for the US market, as some manufacturers are unable to certify where the steel or aluminum in their product was smelted – a requirement for import by anyone.