the no cross over rule applies at events that choose to not have cross overs. Such as nca uca and usa cross overs arent allowed and that is up to them. Companies like cheersport and jamfest allow them. There are not allowed to be any cross overs what so ever at worlds which is why i think some companies have no cross rules.  also, at most competitions that dp allow kids to cross charge a cross over fee or make you pay the origional competition fee.