No government prosecutes every single person who breaks the law. Limited resources make that impossible. District attorneys do not routinely take people to court for possessing small amounts of marijuana; police departments do not generally ticket drivers who speed 1 mph above the limit.
Is immigration enforcement any different? Does the federal government have to crack down on violations uniformly, without exception?
That, essentially, is the question before the Supreme Court, which agreed Tuesday to review the legality of President Barack Obama's executive actions on immigration. Unless the court discovers some as-yet-unknown constitutional principle establishing that immigration law is unlike all other laws, this should be an easy one.
About 11 million people live in the United States illegally. Each year, the federal government deports about 400,000 such individuals. In 2014, Obama sought to focus the government's deportation efforts on those who may actually pose a threat to society.
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He issued an executive order stating that the government would not target individuals whose children are U.S. citizens or lawful permanent residents, who have been in the United States at least since January 2010, and who do not have criminal records. The point was to avoid breaking up families and allow about 4 million people to live without fear of sudden expulsion.
Immigration authorities, Obama said at the time, will go after "felons, not families. Criminals, not children. Gang members, not a mom who's working hard to provide for her kids."
As Obama's legal advisors know well, the president cannot bestow citizenship without statutory authority. What a president certainly can do, as Obama said, is "prioritize, just like law enforcement does every day." As recently as 2012, the Supreme Court reaffirmed this principle.
In United States v. Arizona, the court declared unconstitutional provisions of Arizona's controversial immigration law SB 1070, which allowed the state to detain immigrants who are in the country illegally. The court stressed that only the executive branch of the federal government may decide whether to detain or deport someone who is not lawfully present in the United States. On numerous other occasions, the Supreme Court and lower federal courts have recognized broad prosecutorial discretion to decide when to bring immigration enforcement actions.
Nor has any administration, Republican or Democrat, sought to deport every person who is illegally in the United States. For humanitarian reasons or because of foreign policy considerations or for lack of resources, the government often chooses to not deport undocumented immigrants.
Obama's action is based on exactly such concerns. It is simply impossible to kick out 11 million people, and it is not desirable to separate parents from their citizen children. Children without parents are much more likely to end up in foster care or on the streets or worse.
In 1986, President Reagan and Congress gave legal status to roughly 3 million undocumented immigrants. A year later, Reagan announced that minor children of parents granted amnesty were not subject to deportation. He did this without authorization from Congress.
In 1990, President George H.W. Bush promoted a "family fairness" policy that allowed an additional 1.5 million people, roughly 40 percent of those in the country illegally, to stay. Again, he did this without authorization from Congress. (Today, 40 percent of the undocumented population amounts to 4 million people, or the number Obama protected from deportation.)
The easiest option for the Supreme Court is to rule in favor of the Obama administration by dismissing the case on jurisdictional grounds. A party can sue in federal court only if it demonstrates that it has been injured. But Texas and the 25 other states that brought the lawsuit have a very flimsy argument there -- the administrative costs associated with issuing driver's licenses to newly eligible immigrants. That's just silly; the states could choose not to issue driver's licenses -- that's not an explicit requirement -- or they could choose to charge fees to defray the expense.
Everything about immigration policy is deeply divisive, even -- apparently -- the choice to let parents remain with their children. The issue before the Supreme Court, however, is not whether Obama's actions are wise or beneficial, but whether they are legal. And the answer to that is clear and long settled.
Erwin Chemerinsky, is dean of the University of California, Irvine School of Law.