[M&M Guy]

I'm not sure I've seen a "list" of reasons. I do remember the NFHS coming out with a couple of paragraphs explaining why they wanted this called, and the reason for changing this to a violation from a T is because it wasn't being called enough in their opinion. One of the most common unauthorized reasons is to get around a screen along the sideline or baseline. I believe another reason they gave in the rules was a dribbler being considered OOB by stepping on the line, even though they might not actually be touching the ball at the time. The point I believe they were trying to make was the game needs to stay within the confines of the court, and not try to use "technicalities" to expand the playing area. I remember seeing an extreme example of an unauthorized leaving several years ago in a video of a high school game. The gym had a wall behind the baseline, and there were doors on either side, pretty much like most gyms. During a play, A1 goes running down the sideline, crosses the endline, and goes right out the door. Of course, the defense is standing around going "WTF?!" (source: Dan_ref). A few seconds later, A1 comes back in the door by the other sideline, steps inbounds, takes the pass, and scores before the defense figures out what's going on.

Obviously, falling OOB, say by going after a ball going OOB, or being pushed OOB, is not unauthorized. But purposely expanding the general playing area to include OOB areas is unauthorized. Does that make sense?