User blog comment:Blackendedsoul/The Authority of Admirals/@comment-1595565-20130705234556

The Marines decide who gets to be Shichibukai and if their actions are in accordance enough with whatever special or lightened rules they have set up for them. As we saw with Smoker and Tashigi in Alabasta, it does not take an admiral to revoke their status, since an ensign make the official declaration. The Marines give out the rights, and in turn can take them away, should they deem it necessary.