We utilize several advanced AML data providers to maintain an acceptable level of AML risk on par with other CEX platforms. Our platform's objective is to provide the best service for instant cryptocurrency exchange, but we will never facilitate the laundering of stolen funds or those obtained through hacking, and so forth. When a client creates an exchange request, a unique address is generated for payment. If the client sends cryptocurrency with a high AML risk to this address, the exchange will be immediately suspended by our system. After that, the client will be prompted on the request page to specify a return address and press the "Send" button. After this action, the funds will automatically return to the address from which the payment for the exchange request was made. This system is fully automated.
It's still a bad idea and will probably cause additional problems and doubts about your service.
I'll try one more time. Some services, for example CEX's, casinos etc... use different wallets/addresses for deposits and withdrawals of their users. For example, the deposit goes to the cold wallet and address A (connected with the user account), while the withdrawal is made from the hot wallet and address B. So, in case the user going to withdraw and send BTC directly from his casino account to your exchange, it comes from address B. If you judge that the coins do not pass your AML control, you will return them to address B, which is not exclusively connected to a specific user account.
Everything is automated and not reversible.
The epilogue is that you sent a donation to the casino, and you will claim that you acted fairly, but the user was left without his funds.
The casino in this case is just an example, although coins from there often have an AML problem. Also, sending directly from the casino (or other services) to the exchange is not a good practice, but it happens quite often, so I would not rule out this possibility.
Once a mistake like this happens, you'll be left with negative feedback forever, or you'll be paying out of pocket to cover it up.