T he scope of the executive's discretion in implementing federal immigration law is a topic of perennial interest to Members and committees of Congress. Most recently, questions have been raised as to whether particular actions announced by the Obama Administration in November 2014 are within the executive's authority. However, similar questions were raised in the past about other executive actions including, but not limited to (1) suspending enforcement of certain provisions of the Immigration and Nationality Act (INA) in areas affected by natural disasters; (2) granting deferred enforced departure, extended voluntary departure, or other relief from removal to certain aliens who entered or remained in the United States in violation of the INA; and (3) "paroling," or permitting the entry of, certain aliens into the United States who were not admissible under current law. The debate over whether particular actions are within the executive's authority—acting on its own and without the enactment of additional legislation by Congress—ultimately reflects the respective roles that the executive and legislative branches play in the nation's constitutional system of government. Article I of the Constitution expressly grants the power to legislate to Congress, and Congress has exercised this power as to immigration, in part, by enacting the INA. The INA provides a comprehensive set of rules governing the admission of foreign nationals into the United States and the conditions of such aliens' continued presence in the country, including their eligibility to obtain employment and public benefits, change or adjust their immigration status, and become U.S. citizens. In addition, the INA establishes various mechanisms for enforcing these rules, including by prescribing the removal of aliens found to have entered the United States without permission, or to have violated the terms governing their authorized admission into the country. It also establishes criminal penalties for certain immigration violations. On the other hand, the INA expressly or impliedly confers some discretionary authority on the executive branch in matters of immigration enforcement. For example, the INA authorizes immigration officials to grant certain types of benefits or relief to qualifying aliens who lack lawful immigration status. Moreover, the INA permits immigration officials to waive certain statutory restrictions that might otherwise render an alien ineligible to receive particular immigration benefits. The exercise of these discretionary authorities may enable some unlawfully present aliens to remain in the United States—through asylum, temporary protected status, cancellation of removal, or some other means—rather than being removed. In other cases, however, aliens who have entered or have stayed in the United States in violation of INA requirements may be permitted to remain in the country and, in some cases, legalize their status, not as the result of the exercise of expressly delegated authority, but as a result of the executive branch's independent discretion in enforcing the law. Article II of the Constitution specifically tasks the executive to "take Care that the Laws be faithfully executed," and the executive branch has historically been seen as having some discretion in determining when, against whom, how, and even whether to prosecute apparent violations of the law. For example, immigration officials m ay opt to give a lower priority to the removal of certain categories of unlawfully present aliens because the removal of other categories (e.g., those convicted of serious crimes) has been deemed a higher priority in light of resource constraints and other considerations. Congressional enactments could, however, be seen as limiting the executive's discretion not to take particular actions (e.g., by mandating that certain aliens be detained pending removal proceedings). The express adoption of an executive policy that is "in effect an abdication of ... statutory duty" could also be found to be impermissible, but it might be difficult for a court to assess whether an alleged failure to enforce the law constitutes an abdication. The executive branch's discretion to interpret applicable statutes when Congress has not spoken to the precise question at issue may also afford immigration officials some flexibility in determining how INA requirements apply to a particular alien or category of aliens. This discretion may be relevant in determining how particular statutory grants of discretionary authority are to be applied (e.g., what constitutes "exceptional and extremely unusual hardship" for purposes of cancellation of removal, or "extreme hardship" for purposes of certain waivers of inadmissibility). It can also play a role in determining whether and how particular statutes are seen to circumscribe the executive's enforcement discretion. That is, where a statute is silent or ambiguous as to the circumstances of its enforcement in particular cases, the executive may have some discretion in determining its application. This report provides an overview of the three broad types of discretion that the executive can be seen to have as to immigration. Namely (1) express delegations of discretionary authority; (2) discretion in enforcement (commonly known as prosecutorial or enforcement discretion); and (3) discretion in interpreting and applying statutes. In so doing, it provides notable examples of each broad type of discretion, as well as potential constraints upon the exercise of particular types of discretion. Separate reports discuss prosecutorial discretion in immigration enforcement and the Take Care Clause—which some have suggested constrains the executive's exercise of discretion —in greater detail. See generally archived CRS Report R42924, Prosecutorial Discretion in Immigration Enforcement: Legal Issues , by [author name scrubbed] and [author name scrubbed]; CRS Report R43708, The Take Care Clause and Executive Discretion in the Enforcement of Law , by [author name scrubbed]. In several instances, the INA expressly grants immigration officials some degree of discretion over aliens' eligibility for particular immigration benefits or relief, including adjustment to legal immigration status or authorization to work in the United States. These statutory delegations sometimes provide immigration officials with broad discretion to determine whether and when aliens may be eligible for particular immigration benefits. In other instances, such delegations may permit immigration officials to waive the application of a statutory requirement that would bar otherwise qualifying aliens from obtaining particular immigration benefits or relief. In some instances, the INA expressly authorizes the executive branch to grant certain benefits or relief to aliens. In these instances, aliens are eligible for the benefit or relief not because Congress has given the executive branch discretion to waive restrictions that would otherwise bar the aliens from the benefit or relief, as discussed below (see " Statutory Waivers of Restrictions on Benefits or Relief "), but because Congress has affirmatively provided for certain benefits or relief to be granted. In some cases where Congress has delegated discretionary authority over a particular form of benefit or relief to immigration officials, it has provided clear statutory guidance for when such authority may be exercised. In other cases, there are few, if any, express limits on the authority granted to the executive, although some would argue that prior uses of particular authorities should serve to constrain subsequent uses of this authority. The authority to grant benefits or relief can play a significant role in executive discretion as to immigration, as the examples below illustrate. Temporary protected status (TPS) is a type of relief from removal that Congress has authorized the executive branch to grant to aliens who presently cannot be safely returned to their home countries. Section 244 of the INA imposes a number of conditions upon who may be granted TPS. Specifically, aliens must be from a foreign state that the Department of Homeland Security (DHS) has designated due to an ongoing armed conflict; an earthquake, flood, drought, epidemic, or other environmental disaster; or other "extraordinary and temporary conditions" that prevent aliens' safe return; have been "continuously physically present" in the United States since the effective date of their home country's most recent TPS designation; have "continuously resided" in the United States since whatever date the executive may designate (generally a date that is earlier than the TPS designation date); be generally admissible as an immigrant and not ineligible for TPS (e.g., have not been convicted of specified offenses); register during the period prescribed for registration by the executive branch; and pay any registration fee required by the executive branch. In addition, Congress has provided that TPS is generally to be withdrawn if the alien proves to have been ineligible for such status; has not remained "continuously physically present" since the date he or she was first granted TPS; or fails "without good cause" to register annually. Despite these conditions, a grant of TPS can afford significant relief to individual aliens because aliens with TPS are provided identifying documentation and work authorization by the executive branch, and they cannot be removed while they have TPS. TPS can also be a powerful tool for the executive in crafting immigration policy. For example, TPS could be used to enable aliens who are from countries where large numbers of persons have been displaced, but are unlikely to qualify as refugees, to remain in the United States. Further, while TPS is "temporary," in practice, aliens from designated countries are often able to remain and work in the United States for years, potentially prompting further migration from the country. Another example of discretionary authority to grant benefits or relief conferred by statute involves employment authorization documents (EADs) permitting aliens to work legally in the United States. In general, the INA provides that only specified categories of aliens are eligible to obtain employment in the United States, and Section 274A of the INA bars the hiring or continued employment of "unauthorized aliens." The definition of unauthorized alien found in Section 274A describes an unauthorized alien , in part, as an alien who is not "authorized to be ... employed ... by the Attorney General [currently, the Secretary of Homeland Security]." This language has historically been seen as affording immigration officials at least some discretion to grant EADs to aliens, including those without lawful immigration status. There are no express conditions contained in the INA regarding when the Secretary of Homeland Security may grant work authorization, and the executive branch has promulgated regulations that provide for the issuance of EADs to aliens who have been granted various—and often temporary—forms of relief from removal, including deferred action and deferred enforced departure.