Mr. Nathan Vardi is an associate editor at Forbes Magazine and his news beat is money laundering.  His articles describe how drug dealers have sometimes used American Express, BankAtlantic, Union Bank of California / UnionBanCal and other U.S. financial institutions to launder money:

To help prevent the very kind of money laundering Mr. Vardi’s articles discuss, U.S. financial institutions are required to report suspicious financial activity.  As discussed by my post “Terrorist Financing, Money Laundering & Financial Intelligence Units “, Suspicious Activity Reports must be filed with the Financial Crimes Enforcement Network pursuant to 31 C.F.R. Part 103.18 and 31 U.S.C. §5318 {g}.  U.S. financial institutions must additionally have an effective anti-money laundering program under 31 U.S.C. §5318 (h) (1) and 31 C.F.R. Part 103.120.

As Mr. Vardi’s articles also explain, American Express, BankAtlantic, Union Bank of California and others were investigated  or fined because of shortcomings in their anti-money laundering programs.  American Express for example, was fined $25 million on August 3, 2007 by the Financial Crimes Enforcement Network for inadequately reporting suspicious activity and lacking an anti-money laundering program.  American Express however, ultimately ended up forfeiting or paying a total of $65 million as a government fine in a deferred prosecution agreement announced August 6, 2007.  Meanwhile, BankAtlantic paid a total of $10 million in fines pursuant to its own deferred prosecution agreement announced April 26, 2006.  As a related Financial Crimes Enforcement Network Decision also explained, the $10 million was assessed because BankAtlantic had failed to properly report suspicious activity and maintain its anti-money laundering program.
Pursuant to a deferred prosecution agreement mentioned by a September 17, 2007 press release, Union Bank of California similarly forfeited / paid a total of  $31.6 million to settle claims that it too had violated anti-money laundering laws.  Included in said settlement was a $10 million fine imposed by a September 14, 2007 Decision from the Financial Crimes Enforcement Network.  According to the September 14 Decision, Union Bank of California had failed to maintain internal controls regarding its Suspicious Activity Reports. As the Summary at page 2 of that Decision also explains, Union Bank of California had ignored critically important money laundering indicia:

“Union Bank failed to implement an adequate anti-money laundering program reasonably designed to identify and report transactions that exhibited indicia of money laundering, or other suspicious activity, considering the types of  products and services offered by the Bank, the volume of its business, and the nature of its customers.”

As more fully set forth by my post “Asset Search Indicia For Divorce, Debt Collection & Bankruptcy“, the money laundering indicia are described at pages 19-23 and Appendix “F” of the Bank Secrecy Act / Anti-Money Laundering Examination Manual, and by several other authorities.