The practice of immigration law encompasses a broad range of legal environments, from business immigration law in which lawyers represent corporations seeking to employ foreign born workers to deportation defense which includes representing individuals detained by the federal government seeking release from detention and relief from removal. Immigration lawyers practice in large and small firms, non-profit agencies and government. Immigration law can generally be divided into two large spheres administrative or affirmative practice and deportation defense. Administrative practice involves petitioning the U.S. government to allow a person to migrate to the U.S. on an immigrant or non-immigrant visa or as a refugee. This practice can be further broken down into business immigration, family based immigration and humanitarian based immigration. Deportation defense involves more classic litigation including interviewing and counseling clients, motions practice, legal brief writing, preparing lay and expert witnesses, oral arguments, and appellate practice. Given the high rates of immigration detention and the defensive posture, deportation defense is most like criminal defense in its practice. Business immigration is practiced in large and small firms. The clients are corporations who seek foreign-born workers and the intending immigrant is a third party beneficiary of the process. Other small firms take a wider range of cases in the administrative areas and may also do some deportation defense. There are also a number of immigration lawyers who are solo practitioners and those practitioners tend to focus on administrative practice but also do deportation defense. Lawyers at nonprofit agencies tend to focus on humanitarian based immigration such as political asylum claims, visas for victims of domestic violence, and visas for trafficking victims. Nonprofit lawyers also increasingly do deportation defense as the number of detentions and deportations grows. Some nonprofits and small firms specialize in immigrants' rights, which includes complex federal litigation, writs of habeas corpus and administrative practice. In the government sector, lawyers can work as policymakers, as prosecutors in deportation cases and as legislative aides to members of Congress specializing in immigration legislation.