The way I understand the rules, an individual sailor can lose eligibility to race in ISAF-sactioned events (i.e. everything) for knowingly sailing in a prohibited event (Regulation 19.4). Prohibited events include those that use the term "world" in their name without being approved to do so by the ISAF (19.4.1(c)) and events that are not organized by the ISAF or one of their minions (national authorities, affiliated clubs etc) (19.4.1.(d) and RRS 88.1).

So, as far as I can see, calling the F16 class an international class is not by itself a problem. A problem does arise, however, for individual sailors, if they sail in any event that is organized by a body unaffiliated with the ISAF, such as the F16 Class Authority (regardless of whether they call themselves "international" or not) or any similar national or local group.

This may well also be an issue for the proposed Australian nationals being planned for the coming season, unless it is organized under the auspices of some body affiliated with Yachting Australia.

Mark.