No remesa, no immigration?

With remittances from Mexican workers (both legal and illegal) from the United States to Mexico topping $20 billion this year, the president of Mexico, Vicente Fox, is rightly concerned about any potential drop in what is now Mexico's second largest income sector (exceeded only by oil exports) if future immigration by Mexicans to the United States is impeded by plans to 'wall off' the border between the Gulf of Mexico and the Pacific.

I wonder what would happen if, in the name of the "War on Immigration", the White House ordered the cutoff of money orders and bank transfers to Mexico? (We'd probably have to train cash-sniffing dogs to check the southbound mails...)