So, if any customer disobeys those rules and send Bitcoin from the mixer or any sources that the exchange doesn't want, they will block the persons account and the customer could lose their coins forever.
The exchange are doing so to protect their image too based on the government policies, I guess.
So, when they cease those coins, how sure are we that they will take it to the government?
My own of sensitive in this case first is that the exchange will lock your account (withdrawal access deny) from their site and get you queried about the sources of income transaction to your wallet and that's when they've already sensed it that the bitcoin came from a warned and red flagged sources as mentioned mixer and all that.
So in this case when realized you've fucked up of violating the exchange policies probably unknowingly or otherwise, you can decline that you don't have ideal about the fund so, you'll be called to panel to explain. The exchange might only get to seize the tainted funds and let go other of your funds because there's probability that the funds was wrongly sent to your address without your consent.
Then the exchange doesn't have right to penalized you entirely my seizing the whole of your bitcoin in the address knowing that bitcoin address c an be visible in the crypto blockchains that's liable to mistakenly send funds to wrong address.