Addresses four broad questions: Who is a citizen of the United States? Who else can come to this country? When and why can noncitizens be forced to leave? Who has the authority to answer these questions? These questions prompt us to examine the history of U.S. immigration, the constitutional-statutory-regulatory framework that governs immigration and citizenship law, and the federal agencies that administer it. Also addresses contemporary challenges to, and assertions of, immigrants? rights.