If the DW Pokemon is only released as male, all shiny versions are hacked.
http://www.serebii.net/games/hiddenabilityaccess.shtml this list specifies which events are male only
If the DW Pokemon is released as either male or female, shiny versions that are hatched are okay.
DW Pokemon caught in the entralink forest cannot be shiny.
In short, that Shiny DW Dragonite is legal if hatched.