My problem with using legality as the line is that there are a lot of things which fan consensus says are fic - like out-of-copyright works and historical RPF - that are on extremely firm legal ground, and I personally am of the opinion that *all* fanfic is legally protected so I really don't like defining it that way.

But I accept your choice to make that decision! (Also, am learning that several legally-okay things that I thought consensus agree were fanfic - like anthropomorfic - apparently have less consensus than I thought.)