U.S. immigration law is very complex, and there is much confusion as to how it works. The Immigration and Naturalization Act (INA), the body of law governing current immigration policy, provides for an annual worldwide limit of 675,000 permanent immigrants, with certain exceptions for close family members. Congress and the President determine a separate number for refugee admissions. Immigration to the United States is based upon the following principles: the reunification of families, admitting immigrants with skills that are valuable to the U.S. economy, protecting refugees, and promoting diversity. This fact sheet provides basic information about how the U.S. legal immigration system is designed.