I don’t mean “does his endorsement make it legal”, I mean has he done something law-y to make it legal to download the movie?
Depends who actually “owns” the movie.
It was written and directed by Michael Moore but I believe it is “owned” by the people who funded it…originally Buena Vista films but then bought off of them by Bob and Harvey Weinstein.
This article seems to imply that while Moore supports downloading of his film his saying so does not make it legal.
These are the producers and distributors for F/911. Without knowing the details of the contracts between all the various entities, each of them probably has some interest which is negatively affected by online distribution and presumably each of them would need to surrender that interest before online distribution would be legal. Even then there would most likely be an official online distribution system and distributing it outside of that system would still be illegal.