Actually, the adults must be forced to renounce Islam, publicly. On video, which will be provided to the governments of their countries of origin. You want to become an American? Great - you are welcome! But you cannot remain a Muslim or a Nazi or a Communist and do so.
The problem with this is that islam commands its followers to lie if they can gain advantage by it. (Taqiya)
Their governments would see them as heroes for lying to get into our good graces so that they could kill us later.
No moslem can ever be trusted because of this.
(It is sad but it is true that the only honest moslem is a dead moslem)