Wait... you don't hold the user's private keys in the centralized exchange? I must have misunderstood something in here.
This is also interesting for me. I thought that could not be, and that the user has control, only in the decentralized exchanger.
It could be since it would be ideal if exchanges dont hold keys to user funds but they should.also put a mechanism to retrieve it to the rightful owner if proven. I think its a kind of delimma on the part of exchanges. Imho.