Not your key, Not your coin. They can freeze your fund anytime without your permission.
Since exchanges have begun blocking funds also on the basis of how “clean” they "think" bitcoins are or not, it has become increasingly dangerous to use centralized exchanges. They strive to make users afraid to withdraw funds to their wallets at all, so that later their coins will not be recognized as "dirty". They don't just want to get all our bitcoins and manage them themselves, they want to intimidate users into not wanting to get bitcoins outside of centralized exchanges (where it's not real bitcoins). Real bitcoins are only inside the bitcoin blockchain and nowhere else. And centralized exchanges are trying to gain control over real bitcoins with their division of bitcoins, but they still won’t succeed!
Wow! Another dimension of the story and I never thought or reasoned it from this angle. My idea of the reason exchanges seize or reject their so termed unclean bitcoin is because of the regulations imposed by the government in whose country they operate.
I have long thought that it is the war of the government vs the people and exchange. But right now you are making me believe the exchanges are even the master minders of all these.
But I still have my doubts. Why should an exchange reject a coin or frustrate it's flow knowing so well they will make money from the movement or trading of the coin?