I've decided to become the arbiter of canon. This came about largely because of Star Wars, which is determined to dig its own grave.
With this new power, I can dismiss any event I dislike in any work of fiction. In the future, when someone says that the podrace in The Phantom Menace was stupid, I can say, "That didn't happen. In fact, almost nothing in Episode One is canon."
If a show is good, everything in it is provisionally canon. If bad, then everything has to be personally approved by me. This means that most everything in Star Trek: The Next Generation and DS9 is canon, almost nothing in Voyager is canon, about half the things in The Original Series is canon, and so on.
All of the Star Trek movies are non-canon except Wrath of Khan. The only canon in Star Wars is episode 4, 5, and 6.
PS. Everything involving Section 31 in Star Trek is mostly non-canon. Basically, they're actually a faux-organization designed to satisfy other species' need for intrigue.