Contrary to what some may fear, Syrian refugees cannot easily enter the United States and establish residence. There is, in fact, a very thorough vetting process undertaken before refugees are admitted into the U.S. The process can take up to 24 months. It involves security checks by law enforcement, the Pentagon and the intelligence community. Syrian refugees are subject to an even more enhanced security clearance process than are other refugees. For a more detailed explanation of this vetting process read this Wall Street Journal article.