The Trump administration recently adopted a "zero tolerance" policy under which undocumented immigrants apprehended by federal officials are forcibly separated from their children. In April and May alone, almost 2000 children were torn from their parents and detained separately, often under cruel conditions likely to cause trauma and inflict longterm developmental damage. Attorney General Jeff Sessions claims that separation of families is justified by the need to enforce the law, and even asserts that the administration's policy is supported by the Bible. I will leave the Biblical issues to theologians and cardinals, who have addressed them far better than I could. But Sessions' secular argument is no better than his religious one. There is no law requiring family separation at the border. And even if there was, that still would not be enough to justify the administration's cruel policy.
The federal law criminalizing "improper entry" by aliens does not require family separation. The law also provides for the use of civil penalties, as well as criminal ones. While it states that the application of civil penalties does not preclude application of criminal ones, it also does not compel federal prosecutors to pursue both. Until the administration's recent policy change, civil proceedings were in fact the usual approach in case of families with minor children, under both Democratic and Republican administrations. The use of civil proceedings generally does not require pretrial detention, and therefore obviates the need to detain either parents or children; some civil defendants were detained, nonetheless, but in facilities where families can stay together. The Trump administration, by contrast, has sometimes even forcibly separated children from migrants who have not violated any law, but instead have legally crossed the border to petition for asylum in the United States.
The Trump administration claims that their policy is required by the 1997 Flores court settlement. But that settlement in no way mandates family separation and detention of children away from their parents. To the contrary, it instructs federal officials to "place each detained minor in the least restrictive setting appropriate" and to release them to the custody of family or guardians "without unnecessary delay." The settlement also mandates that federal immigration officials must "treat all minors in its custody with dignity, respect and special concern for their particular vulnerability as minors." Detaining children under harsh conditions, separated from their parents, is pretty obviously not "the least restrictive setting" possible, and it most definitely doesn't qualify as treating children with "dignity, respect and special concern for their particular vulnerability."
Even if the law did clearly direct criminal prosecution combined with automatic family separation in pretrial detention, it does not follow that the administration had a legal duty to adopt a "zero tolerance" policy that prioritizes prosecution of this particular type of offense. In a world where the vast majority of adult Americans have violated federal criminal law at some point in their lives, and there are so many laws and offenders that prosecutors can only target a small fraction of them, federal officials inevitably have vast discretion in determining which offenses to pursue and to what degree. First-time illegal entry into the United States is a mere misdemeanor carrying a penalty (up to 6 months imprisonment or a small fine) lower than the penalty for possession of small amounts of marijuana (1 year). The relative penalties suggest that federal law considers the latter a more serious offense than the former. Yet not even hard-core drug warriors like Sessions urge the federal government to adopt a "zero tolerance" policy under which we routinely prosecute all small-time marijuana users. In practice, the feds only target a tiny fraction of them. And when they do, they don't separate their children from them, and detain the children under harsh conditions.
The administration's zero tolerance policy, therefore, is not mandated by law. They could easily exercise the discretion to avoid prosecution and family separation, as previous administrations have, and as the Trump administration itself does in the case of nearly all small-time marijuana users. Prioritizing this offense over nearly all others is a policy choice, not a legal requirement. It's a choice the president made, and one he could reverse at any time.
If enforcing the law really were the main concern of Trump and Sessions, they could easily address the issue by supporting legislation banning family separation at the border, except in cases of child abuse or similar exigency. Congressional Democrats have in fact proposed such a law, the Keep Families Together Act. If Trump were to endorse it, the bill could easily attract enough GOP support to get through Congress quickly, as many Republicans also oppose family separation and worry that the administration's policy might hurt their chances in the midterm elections. But Trump refuses to do that, because he instead prefers to use the plight of separated children as leverage to extract concessions from Congress on other immigration issues. He literally wants to hold the children as political hostages in order to push through his agenda of drastically reducing legal immigration, as well as illegal.
In sum, no law requires the administration's policy, and it is highly unlikely that legal considerations are the true motives for it. But even if the law really did mandate the family separation policy, and legal reform were politically infeasible, that still would not be enough to justify family separation.
Not every law is just. Some, at least, are so unjust that there is no moral obligation to obey them. For example, there is widespread agreement that civil rights activists were justified in violating segregation laws, and abolitionists in violating the Fugitive Slave Acts. Violation of these laws was just because they inflicted grave harm on innocent people based on morally irrelevant characteristics: race and ancestry. Much the same is true of many of our immigration laws. Most of the undocumented migrants entering the United States with their minor children are fleeing violence, abuse, oppression, dire poverty, or other terrible conditions. The laws that bar their entry are largely based on immutable conditions similar to race: who their parents were, or where they were born. The US may not be responsible for the awful conditions these people are fleeing. But if we forcibly deport them back to places where they are likely to face oppression, privation, and often even death, we become complicit in the wrongs they suffer. As philosopher Michael Huemer explains, the situation the situation is akin to one where we use force to prevent starving people from buying food they need to survive.
Most Americans routinely violate laws far less oppressive than segregation laws. For example, the vast majority violate speeding laws, and some 52% admit to using marijuana at some point in their lives. The point is not just many Americans violate these types of laws, but that they believe (rightly) that they commit no wrong in doing so, long as the speeding or marijuana use did not endanger innocent third parties. The same reasoning applies to undocumented migrant families fleeing oppression, except that their illegal actions are motivated by far greater need, and pose much less risk to third parties than speeding does.
Jeff Sessions contends that migrants fleeing horrible conditions should "apply lawfully [and] wait your turn." This admonition might have some validity if they actually had a realistic chance of gaining legal entry in the near future. In reality, the wait time for most potential immigrants who do not have very close relatives in the US is likely to be decades or even centuries. If they apply for asylum, they face a system that refuses to grant it even for many who are victims of horrific violence and oppression, and features Kafkaesque rules such as classifying performing slave labor for guerrillas as providing "material support" to terrorists (thereby making the escaped slave ineligible for asylum). Moreover, Sessions and his political allies have for years resisted all efforts to make legal entry into the United States easier. They have themselves to blame for creating the conditions under which many undocumented immigrants have no plausible moral obligation to obey the law.
Even in the case of otherwise just laws, there must be moral limits to the means used to enforce them. The child-separation policy crosses any reasonable line. It inflicts harm grossly disproportionate to any offense. And most of that harm is suffered by children - people themselves innocent of wrongdoing. Even if their parents acted wrongly in trying to enter the United States, the children had little choice in the matter.
Some try to justify the administration policy by pointing out that people convicted of crimes are often imprisoned in ways that keep them apart from their children. But, in such cases, the children are left in the custody of relatives or guardians chosen by the family, not housed in harsh detention facilities. In addition, it is extremely rare for first-time offenders charged with misdemeanors to be subjected to prolonged detention at all, or even to get prison sentences after conviction (as opposed to fines or probation). If the government started rounding up small-time marijuana users or violators of speeding laws, putting them into pretrial detention, and separating them from minor children who are then placed in confinement under cruel conditions, there would be an outcry. Few, if any, would seriously claim that the policy is justified because it strengthens enforcement of drug and traffic laws. Even most who believe that our marijuana laws and traffic laws are just would condemn such a cruel policy. The same logic applies to Trump's family separation policy at the border.
UPDATE: I have made some minor additions to this post.