User blog comment:Ghmorello/Chapter 903: News Recap, Followed By Our Live Coverage Of The Reverie./@comment-156.205.48.247-20180428123219/@comment-97.81.27.42-20180428202408

I do not know what the traditional procedure it is for an island to be the official territory of a Yonko, but Neptune did say to Jinbe that in case they "lose" the Big Mom flag that they would use Luffy's Jolly Roger.