Does it apply to where you've just been unshipped, as well? That strikes me as unfair if it does, since if your horse just "banished you from the saddle" as I heard it described recently, and didn't slip, spraddle, or fall, then it seems reasonable to climb back aboard if you can. But for sure, if the horse has fallen, I'd not wish to see it remounted, not even for a lazy canter back to the stables, as Ruby is guilty of doing on several occasions, and which I still see happen in Ireland. It doesn't matter how soft the fall is - tissue damage might've occurred, and you're only adding to the damage by putting your weight on the horse and asking it to go on.