Modern Islamic banks are overseen by the Shari'a Supervisory Board of Islamic Banks and Institutions ("The Shari'a Committee").
The Shi'a "Islamic Laws according to the Fatawa of Ayatullah al Uzama Syed Ali al-Husaini Seestani" has this to say about Hawala banking: "2298. If a debtor directs his creditor to collect his debt from the third person, and the creditor accepts the arrangement, the third person will, on completion of all the conditions to be explained later, become the debtor.
Thereafter, the creditor cannot demand his debt from the first debtor".
The prophet Muhammad (a cross border trader of goods and commodities by profession) encouraged the free movement of goods and the development of markets.
Numerous Moslem scholars railed against hoarding and harmful speculation (market cornering and manipulation known as "Gharar"). Moslems were the first to use promissory notes and assignment, or transfer of debts via bills of exchange ("Hawala"). Among modern banking instruments, only floating and, therefore, uncertain, interest payments ("Riba" and "Jahala"), futures contracts, and forfeiting are frowned upon. But agile Moslem traders easily and often circumvent these religious restrictions by creating "synthetic Murabaha (contracts)" identical to Western forward and futures contracts. Actually, the only allowed transfer or trading of debts (as distinct from the underlying commodities or goods) is under the Hawala. "Hawala" consists of transferring money (usually across borders and in order to avoid taxes or the need to bribe officials) without physical or electronic transfer of funds.
Money changers ("Hawaladar") receive cash in one country, no questions asked. Correspondent hawaladars in another country dispense an identical amount (minus minimal fees and commissions) to a recipient or, less often, to a bank account. E-mail, or letter ("Hundi") carrying couriers are used to convey the necessary information (the amount of money, the date it has to be paid on) between Hawaladars. The sender provides the recipient with code words (or numbers, for instance the serial numbers of currency notes), a digital encrypted message, or agreed signals (like handshakes), to be used to retrieve the money. Big Hawaladars use a chain of middlemen in cities around the globe.
But most Hawaladars are small businesses. Their Hawala activity is a sideline or moonlighting operation. "Chits" (verbal agreements) substitute for certain written records.
In bigger operations there are human "memorizers" who serve as arbiters in case of dispute. The Hawala system requires unbounded trust. Hawaladars are often members of the same family, village, clan, or ethnic group. It is a system older than the West. The ancient Chinese had their own "Hawala" - "fei qian" (or "flying money"). Arab traders used it to avoid being robbed on the Silk Road.
Cheating is punished by effective ex-communication and "loss of honour" - the equivalent of an economic death sentence. Physical violence is rarer but not unheard of.
Violence sometimes also erupts between money recipients and robbers who are after the huge quantities of physical cash sloshing about the system. But these, too, are rare events, as rare as bank robberies. One result of this effective social regulation is that commodity traders in Asia shift hundreds of millions of US dollars per trade based solely on trust and the verbal commitment of their counterparts.