There are plenty of FBI docs that get released by journalists and others who are not FBI agents, so it's hard to take that as a given without seeing the tweets in context, which I did not see. The ruling does mumble something about the account passing itself as an FBI agent, as I've since had a chance to read, but it doesn't give any details and I didn't see any mention of that law.

Also, I'm surprised the NPR ran this article, given the disclaimer at the bottom that it's a party to it. Usually the lawyers just don't let you do that.