Slave country help (White Giant)

Um, I won a war against a leaderless country. I would like to know how to set them free. The only reason I have them in my empire is because I wanted to transfer their weopons and money to my country. So how can I just dith them

Click "add country or enterprise" in the left menu, when logged into that country. The removal option is in there.

On the top of the page:

"general" - "registration" - Cancel your country"