All responsibility for the transaction lies with the sender and the receiver because they know the purpose of the payment. The person who provides your channel in the lease do not have to know the purpose of the payment. When you provide a car in rent you are not responsible for the illegal actions of the driver. Law enforcement agencies need to prove that you are part of the system. By default, you are only a tool.
I could also add to this example another one, which seems to be more fitting here. If you use your bank account to send someone money which was obtained via or intended for some illegal activity, will the bank be held responsible for sending your funds? I'd rather say no in this case but, and this is a big but, we should never say never because there can be ramifications which may render this logic totally irrelevant and void due to an arbitrary number of reservations in the law.