	Introduction

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 the enforcement of federal immigration law, which is largely contained in the Immigration and Nationality Act of 1952 (INA), as amended . 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, and immigration officers appear to have exercised such discretion in individual cases and on a categorical basis for decades. For example, the Kennedy Administration granted extended voluntary departure to persons from Cuba in 1960, allowing many otherwise deportable Cuban nationals to remain in the United States for an extended period, while the George W. Bush Administration temporarily suspended employer sanctions on entities that employed unauthorized aliens in areas affected by Hurricane Katrina. In addition, in some cases, the Supreme Court has suggested that federal regulation of immigration is grounded in the federal government's "inherent power as a sovereign to control and conduct foreign relations." Many, although not all, of these powers belong exclusively to Congress, and courts and commentators have sometimes used language which implies that Congress is preeminent in the field of immigration. Few courts or commentators have, however, directly addressed the separation of powers between Congress and the President in the field of immigration, and in some cases, the Court has also suggested that the executive branch shares plenary power over immigration with Congress as one of the "political branches." However, the executive branch's authority to exercise prosecutorial or enforcement discretion has traditionally been understood to arise from the Constitution, as discussed below. These decisions include
whether to parole an alien into the United States; whether to commence removal proceedings and what charges to lodge against the respondent; whether to pursue formal removal proceedings; whether to cancel a Notice to Appear or other charging document before jurisdiction vests with an immigration judge; whether to grant deferred action or extended voluntary departure; whether to appeal an immigration judge's decision or order, and whether to file a motion to reopen; whether to invoke an automatic stay during the pendency of an appeal; and whether to impose a fine for particular offenses. Potential Limits on the Exercise of Discretion

While prosecutorial discretion is broad, it is not "unfettered," and particular exercises of discretion could potentially be checked by the Constitution, statute, or agency directives. However, no court appears to have invalidated a policy of non-enforcement founded upon prosecutorial discretion on the grounds that the policy violated the Take Care Clause, and one federal appellate court has opined that "[r]eal or perceived inadequate enforcement ... does not constitute a reviewable abdication of duty." However, the Heckler Court also noted that this presumption of nonreviewability "may be rebutted where the substantive statute has provided guidelines for the agency to follow in exercising its enforcement powers." Were that the case, DHS's exercise of prosecutorial discretion could potentially be found to have been constrained by its own guidelines.
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.
Certain decisions have been widely recognized as within the prosecutorial discretion of immigration officers. These include deciding whether to initiate removal proceedings and what charges to lodge against the respondent; canceling a Notice to Appear or other charging document before jurisdiction vests with an immigration judge; granting deferred action or extended voluntary departure to an alien otherwise subject to removal (deportation); appealing particular decisions or orders; and imposing fines for particular offenses, among other things. Enforcement priorities and resources, as well as humanitarian concerns, have typically played a role in determining whether to exercise discretion in individual cases. For example, the George W. Bush Administration temporarily suspended employer sanctions in areas affected by Hurricane Katrina, and the Obama Administration recently began granting deferred action to certain unauthorized aliens brought to the United States as children.
While the executive branch's prosecutorial or enforcement discretion is broad, it is not unfettered, and particular exercises of discretion could potentially be checked by the Constitution, statute, or agency directives. Selective prosecution, or prosecution based on race, religion, or the exercise of constitutional rights, is prohibited, although aliens generally cannot assert selective prosecution as a defense to removal. A policy of non-enforcement that amounts to an abdication of an agency's statutory responsibilities could potentially be said to violate the Take Care Clause. However, standing to challenge alleged violations of the Take Care Clause may be limited, and no court appears to have invalidated a policy of non-enforcement founded upon prosecutorial discretion on the grounds that the policy violated the Take Care Clause. Non-enforcement of particular laws could also potentially be challenged under the Administrative Procedure Act if a statute provides specific guidelines for the agency to follow in exercising its enforcement powers. In addition, an agency could potentially be found to have constrained its own discretion, as some courts found that the INS had done in the 1970s with its operating instruction on deferred action.