Presumably all money can be traced if somebody is interested, and takes enough time and trouble to do it. The point of money laundering is to make that process difficult.
The idea here was that the perp--in reality an FBI agent--would be able to say, if asked about the funds in his Long Island account, that he didn't have to answer questions because he was protected by attorney-client privilege.
Of course it didn't work, because it was lame. And as Kaja Whitehouse pointed out, the idiot Scaglione probably got the idea from Breaking Bad.