What is the ruling on borrowing money earned through illicit means, such as "Saudization" (i.N. using a Saudi national as a front for a business run by a foreigner) and fraud?

Money earned through unlawful means, such as fraud and the like, is forbidden for the one who acquires it. The prohibition is tied to the person's responsibility, not to the money itself. Therefore, many scholars hold that it is not forbidden to engage in transactions involving such money, like borrowing, or other dealings.