Presidential candidate Donald Trump announced Tuesday his plan to force Mexico to pay for his planned wall at the border. The controversial businessman turned Republican frontrunner said that his administration would use a U.S. anti-terrorism law to cut off certain money transfers from the United States to Mexico. More specifically, Trump said that he wants to cut off remittances from illegal immigrants sending money back to their families in Mexico. Today’s memo from the Trump campaign called these remittances a “de facto welfare for poor families in Mexico.” According to a study from the World Bank, cash flow from the U.S. to Mexico via remittances was nearly $24 billion in 2014, the last year from which it has full data. According to the Trump campaign, most of that money is in the U.S. illegally, although the World Bank said that was unclear. President Obama responded to Trump’s memo today, saying that the idea was impractical. "The notion that we're going to track every Western Union bit of money that's being sent to Mexico, you know, good luck with that," Obama said. Obama specifically drops a company name: Western Union WU. Western Union, along with Moneygram MGI, and PayPal’s PYPL Xoom service are all methods of transferring money internationally. These services get a large slice of their business from people trying to move cash. Sometimes that comes from less-than-legal sources, as the Trump campaign points out, but it is an undeniable aspect of the business. If Trump gets a chance to put his plan in place, these stocks could take a hit. Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report >>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report MONEYGRAM INTL (MGI): Free Stock Analysis Report WESTERN UNION (WU): Free Stock Analysis Report PAYPAL HOLDINGS (PYPL): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research