President Obama is reportedly considering “deferring” (temporarily suspending) the deportation of up to five million unauthorized immigrants, which would expand and be modeled after his 2012 Deferred Action for Childhood Arrivals (DACA) initiative. This has led to a stimulating and lively public discussion regarding the extent of the president’s legal authority under U.S. immigration law. Understanding the basics of what the president may or may not do under existing law, his constitutional authority and responsibilities, and what Congress can do about it if it disapproves of the president’s course of action, is essential for evaluating the various policy arguments and should help non-lawyers follow the many nuances of this substantive debate.

Here are four questions and answers to get you up to speed:

1. Does the president have legal authority to defer the deportation of all unauthorized immigrants?

No. The president cannot refuse to enforce immigration laws, or enforce an immigration law in a way that is contrary to the aims of the law, or change immigration policy on his own. This requirement comes from the “Take Care” clause in the U.S. Constitution, which requires the president to ensure “that the Laws be faithfully executed” (Article II, Section 3). The Immigration and Nationality Act, the United States’ main set of immigration laws, contains many provisions specifying who is a “removable” (i.e., deportable) migrant (the term the law uses is “alien”). Right now there are an estimated 11.7 million unauthorized immigrants in the United States, who are deportable unless they can prove that they deserve to remain in the country because they are entitled to a legal status under U.S. law.

Congress provides the executive branch the funds to enforce the immigration laws, but it has not provided nearly enough funding to deport all 11.7 million unauthorized immigrants. The Department of Homeland Security (DHS) believes that the amount Congress has appropriated is enough to deport approximately 400,000 unauthorized immigrants per year (3.4 percent of the total) and that is how many people the Obama administration has been deporting. If the president were to refuse to deport any unauthorized immigrants, such action would violate his constitutional duty to faithfully execute the laws and amount to a de facto legalization in direct contradiction of what Congress has required of the president.

2. Does the president have legal authority to defer the deportations of certain unauthorized immigrants?

Yes. The president has leeway to enforce the law—be it criminal, tax, or in this case, immigration law—in the manner he determines will be most likely to achieve the aims of the law being enforced. This is known as “prosecutorial discretion.” While some scholars disagree as to the scope and parameters of prosecutorial discretion, none can reasonably argue that the president lacks this authority, and the U.S. Supreme Court affirmed the president’s use of prosecutorial discretion in the context of immigration specifically in Arizona v. United States.

This doesn’t mean the president can decline to deport a particular unauthorized immigrant without justification; such a decision must be made in the context of enforcement priorities that are consistent with the policy goals of the law being enforced. Thus, the president can decide whom to deport first, and whom to deport last, as well as everyone in-between, by order of importance. Anyone granted “deferred action” has simply been put at the end of the list for deportation. The president (or DHS, which implements his policies) can decide to change an unauthorized immigrant’s place in the deportation line without needing to specify a reason. That’s why any deferred action is temporary and reversible. It is the government telling an unauthorized immigrant, “we’re not going to deport you right now, because there are others it’s more important to deport first,” but deferred action does not lead to or confer any other immigration status such as permanent residence or citizenship.

Deferred action is also the government making the sensible decision to focus its deportation efforts on the least desirable of the unauthorized immigrants—like criminals and individuals who pose national security risks, especially. It would be irrational and inefficient enforcement policy if the president did not set priorities regarding who should be deported first. The statutory objective set out in the law is the deportation of unauthorized, deportable immigrants, and DHS believes the appropriations it receives from Congress (which reflect Congress’ budgetary and enforcement priorities) allow DHS to deport about 400,000 unauthorized immigrants per year. It is a matter of common sense that the president should set enforcement priorities, which means deciding the characteristics of the unauthorized immigrants that will be deported first. (The president’s current deportation priorities are set out in detail in the Morton Memo of March 2, 2011, a guidance memo from U.S. Immigration and Customs Enforcement; they include unauthorized immigrants who pose a danger to national security or a risk to public safety, including convicted criminals, who are recent entrants or border crossers who entered the United States without authorization, and/or who are fugitives or who otherwise obstruct immigration controls.)

Again, because there are 11.7 million unauthorized immigrants in the United States, but DHS will only deport up to about 400,000 per year, the president may decide the characteristics of unauthorized immigrants who are considered low priorities, such as those who qualify for the DACA initiative (young people without criminal records who entered the United States as children before 2007 and meet other requirements), and those with characteristics similar to the ones delineated in the Morton Memo of June 17, 2011, which include an unauthorized immigrant’s family ties to U.S. citizens, length of presence in the United States, pursuit or completion of a university education, or service in the military.

3. Does the president have legal authority to grant work permits to unauthorized immigrants?

Yes. Under existing law, the president has the authority to grant work authorization (also known as an Employment Authorization Document or EAD) to any unauthorized immigrant in the United States. This is set out in the Immigration and Nationality Act, at Section 274A(h)(3) [8 U.S.C. 1324a(h)(3)]. This provision passed Congress and was signed into law by President Reagan as part of the 1986 Immigration Reform and Control Act, which legalized a large portion of the unauthorized immigrant population at the time and created the “I-9” employment verification system (anyone ever hired for a job has probably filled out an I-9 form). Not all current members of Congress agree that the president should have this power; for example, in 2011, then-chairman of the House Judiciary Committee Lamar Smith (R-Texas) introduced H.R. 2497, the “Hinder the Administration’s Legalization Temptation” Act (the “HALT Act”), which would have repealed the president’s authority to grant EADs to anyone he deems appropriate. But the HALT Act did not pass, in fact it was not even voted on in either chamber of Congress, so no one can seriously claim that the president does not have the requisite legal authority to grant employment authorization.

4. Can the president be sued in court for using prosecutorial discretion to decide how to prioritize deportable unauthorized immigrants?

It’s unlikely that the president could be successfully sued for exercising prosecutorial discretion and granting deferred action to a subset of the unauthorized immigrant population. Any plaintiff seeking to sue the president would need to have “standing” in federal court, which means the plaintiff suing the president must show that he or she has: 1) suffered an injury-in-fact or will be imminently injured, 2) that there is a causal connection between the injury suffered and the action of the president; and 3) that a court decision in favor of the plaintiff will redress the injury suffered by the plaintiff.

If the president decides to defer the deportation, for example, of 5 million unauthorized immigrants who have been in the country for at least 10 years, have an immediate U.S.-citizen relative, and have not committed any serious crimes—in this scenario who can claim they have been injured by this action? How has any member of Congress or the public suffered by the non-deportation of an otherwise law-abiding resident or worker who has been in the country for a decade? It’s difficult to even come up with a hypothetical example. Proving that a plaintiff has standing will be a major obstacle to any lawsuit being filed against the president for offering deferred action to certain unauthorized immigrants.

In addition, federal courts are generally reluctant to resolve disputes between the executive and legislative branches of the government. Such a dispute would likely be considered a “political question” by the court. Political questions are “nonjusticiable” (i.e., cannot be adjudicated) because the court is not being asked to resolve a legal dispute, which is its function, but is instead being asked to decide on an issue that can be resolved through the political process. The specific elements for what constitutes a political question are described in a landmark U.S. Supreme Court case, Baker v. Carr (369 U.S. 186 (1962)), but the key in this immigration context is that in response to an action taken by the president that Congress objects to (for example, expanding DACA), Congress could pass a law that constrains or further specifies how it wishes to see the president enforce U.S. deportation laws, or Congress can deny funding for the president’s actions through the appropriations process, or both. Thus, there is a clear political solution and pathway to resolve the problem that some members of Congress are complaining about (i.e., that the president is not enforcing the law properly or at all), but Congress has so far declined to go down that path. As a result, the president may enforce the laws as he sees fit, so long as his actions further the goals of the laws he is enforcing and do not blatantly contradict or ignore them.

Using prosecutorial discretion to enforce the law according to clear priorities, the president is on solid legal ground if he wishes to defer the deportation of an expanded subset of unauthorized immigrants beyond those eligible for DACA. But it is also clear that the president cannot refuse to deport all 11.7 million unauthorized immigrants, or come too close to declining to deport all 11.7 million, because that would violate his duty to enforce the law under the Take Care clause of the Constitution. If, as is rumored, the president uses deferred action to suspend the deportation of 5 million unauthorized immigrants, it would cover 43 percent of the total unauthorized population, but leave nearly 7 million unauthorized immigrants still subject to deportation. If the deportation rate of approximately 400,000 per year continues, it would take almost 17 years to deport the remaining 7 million unauthorized immigrants, assuming no new migrants entered the country without authorization or overstayed the validity period of their temporary visas. That’s why if such action is taken, the president’s challenges will be political rather than legal.