Prosecutorial Discretion in Immigration Enforcement: Legal Issues [January 17, 2013] [open pdf - 400KB]
"The term 'prosecutorial discretion' is commonly used to describe the wide latitude that prosecutors have in determining when, whom, how, and even whether to prosecute apparent violations of the law. The Immigration and Naturalization Service (INS) and, later, the Department of Homeland Security (DHS) and its components have historically described themselves as exercising prosecutorial discretion in immigration enforcement. Some commentators have recently challenged this characterization on the grounds that DHS enforces primarily civil violations, and some of its components cannot be said to engage in 'law enforcement,' as that term is conventionally understood. However, even agencies that do not prosecute or engage in law enforcement have been recognized as having discretion (sometimes referred to as 'enforcement discretion') in determining whether to enforce particular violations. Federal regulation of immigration is commonly said to arise from various powers enumerated in the Constitution (e.g., naturalization, commerce), as well as the federal government's inherent power to control and conduct foreign relations. Some, although not all, of these powers belong exclusively to Congress, and courts have sometimes described Congress as having 'plenary power' over immigration. However, few courts or commentators have addressed the separation of powers between Congress and the President in the field of immigration, and the executive has sometimes been said to share plenary power over immigration with Congress as one of the 'political branches.' Moreover, the authority to exercise prosecutorial or enforcement discretion has traditionally been understood to arise from the Constitution, not from any congressional delegation of power."
CRS Report for Congress, R42924