There’s a reason New York and London continue to be world leaders in processing financial transactions–the governments have been intentionally tolerant of shady characters, shady businesses, and shady nations as long as the transactions nominally followed the law. Among other benefits, that puts you in a good position to keep track of the bad guys and, when it really counts, to take them down. If you police too heavily all that activity goes somewhere else.
.. Like so much with the War on Terror, the better approach would be to improve HUMINT and investigatory resources, rather than pushing the activity further underground and playing a game of whack-a-mole.