Mexican drug lords and international money launderers have partnered together to transfer illicit cash through an ancient off-the-books system known as a hawala originating in the Muslim world which now are operating in the United States according to a federal indictment as reported by Joel Rubin for the Los Angeles Times:
At the center of a hawala are brokers who receive cash from clients looking to transfer the funds to a person in another city or country. That broker -- called a hawaladar -- then contacts a trusted hawaladar near the recipient and instructs him to pay the recipient. Hawaladars do not use written contracts to document their transactions, the indictment said. And they are careful to keep the amount of the credits and debts they have with each other in balance to avoid the need to transfer actual cash to settle debts. Variations of the hawala system are used widely in Afghanistan, India and other countries in lieu of official banks to make both legal and illicit transactions.
The hawala system also often is used to finance terrorist activities.