In some respects,
it doesn't matter - the 15 year old French student
will be subject to TSA regulations on departing the US, and strike-anywhere / non-safety matches seem to be a no-no, as you say, carried on or checked in. (Thanks, Richard Reid, for being an idiot about where you chose to light up our lives.

) BTW, these matches are also prohibited from being carried on in the EU, but not mentioned in regard to checked luggage.
In partial reply to your initial query:
European Union carry-on regulations from EU Europa website.
Links to various EU airport security regulation PDF pages from EU Europa website.