legality versus morality
Immigration from one nation to another is not intrinsically evil. The Holy Family immigrated to Egypt from the Holy Land. The Apostles immigrated to various distant nations to spread the Gospel. The faithful have often, throughout the history of the Church, moved to other nations, even permanently, so as to bring the true Faith to the whole world. Therefore, immigration is not inherently immoral.
When immigration is illegal, it may or may not remain moral.
There are three fonts of morality. If the person has only good intentions when immigrating, the first font (intention) is good; the act is not a sin due to a bad intention, even if the immigration is illegal. The passing of a law by civil society does not determine the intention of the person who acts. However, if someone were to immigrate, legally or illegally, with the intention of committing a crime or a sin, the act of immigration would be sinful.
Since immigration is not intrinsically evil, it cannot become intrinsically evil by being made illegal. The passing of a law by civil society does not change the moral object, nor the eternal moral law. So the second font of morality (moral object) remains good, even when the immigration is illegal.
However, the third font of morality (circumstances) is changed by the passing of a law making an act illegal. An illegal act has some bad consequences that result from its illegality; these bad consequences would not be part of the circumstances if the act was legal.
For example, if a priest commits the moral act of protesting abortion, but he does so in a way that is illegal, the consequences of breaking the law must be weighed in the third font. If breaking the law will result in a long jail sentence that will deprive his congregation of the great spiritual benefits of his priestly ministry, the bad consequences of the protest might outweigh the good consequences.
So an act that is moral, when it is legal, might become immoral, when it is made illegal, due to additional bad consequences in the third font of morality.
However, in the case of illegal immigration, if the law is not well enforced, and the penalty is mainly return to one's own nation, then the dire need for work to support one's family might result in the good consequences of illegal immigration outweighing the possible bad consequences. Therefore, many acts of illegal immigration are not immoral. All three fonts of morality are good, and so the act is morally permissible.
intrinsically unjust laws
Even though many acts of illegal immigration may be moral, a nation has a responsibility to govern its borders. A set of laws governing immigration, making some types of immigration illegal, is not an intrinsically unjust law. The fact that it may be moral to violate a law in some circumstances does not necessarily imply that the law is evil.
However, a law addressing the problem of illegal immigration can possibly be intrinsically evil, in a number of different ways.
1. excessive harm - If any act can be reasonably anticipated to do more harm than good, the choice of that act is a sin (because the third font is bad). A law that, due to certain circumstances, does more harm than good is an unjust law.
If a nation has 10 illegal immigrants, all 10 might be returned to their native land without any grave harm. We can reasonably anticipated that all 10 might find work and a place to live in their own nation. (We should not return persons to their own nation if we reasonably anticipate that they will suffer grave harm unjustly, such as persecution or death.)
But the U.S. currently has over 10 million illegal immigrants. We cannot return them to their own nation, because we can reasonably anticipate that grave harm will occur to many persons if we do. There are not 10 million homes and 10 million jobs waiting for those persons in their native lands. And even if such were the case, to uproot 10 million persons and move them a great distance causes a severe disruption to a vast number of lives (not only to the lives of those uprooted). Any act that can be reasonably anticipated to do more harm than good is a sin. Much harm, and little good, would be done by deporting 10 million persons. If the reasonably anticipated bad consequences gravely outweigh the good consequences, then the act is gravely immoral; it is an objective mortal sin.
If the U.S. were to attempt to deport the 10 million illegal immigrants, we could reasonably anticipate that many of those persons would die. The nations to which they would be deported generally do not have social safety net programs. And even if they did, a flood of 10 million persons would break those programs. Many would die. It would be like the Cherokee Trail of Tears. They would return to their own nations without a place to live; most would not be able to obtain work. They would not have adequate food or shelter. They would easily fall ill; there would be little or no medical care for them. They would easily fall prey to crimes of violence. If only one percent of those 10 million die as a result of such a massive deportation, there would be 100,000 deaths. But the percentage could easily be much higher than one percent. And those who do not die would nevertheless be likely to suffer grave harm by being uprooted from their lives in the U.S., by being deported to a place where they lack homes, work, income, food, and medical care. Such extensive harm to so many persons gravely outweighs any good that might be accomplished. Therefore, such a massive deportation would be a grave sin.
2. excessive punishment - The punishment of a guilty person, by proper authority, in proportion to his guilt, is moral. However, the punishment of a guilty person in substantial excess, beyond what his guilt deserves, is the punishment of an innocent person. Every guilty person is innocent beyond the measure of his guilt. Excessively harsh punishments for moral but illegal immigration is intrinsically evil. Any law that requires punishments of the guilty in substantial excess of their guilt (or without determining their guilt or innocence by a just process) is an intrinsically unjust law because it seeks to punish the innocent.
Illegal immigration, except for the purpose of committing a grave crime or grave sin, is a relatively minor offense (and often not a sin at all). It would be unjust and sinful to punish illegal immigrants, those who are not committing some additional grave crime, with a harsh penalty for such a limited offense. Even a substantial jail sentence would be an excessive punishment for such a limited offense.
Recently in the U.S., various laws in various states have been proposed or enacted which would: deny illegal immigrants a reasonable path to citizenship, deny them health care, deny them education, deny them work, deny them the ability to rent or buy a place to live, deny them a license to drive a vehicle, deny them assistance when in great need (from social safety net programs). These laws represent a very grave punishment for a relatively light offense. These laws are therefore intrinsically evil and must be opposed by all faithful Catholic Christians. But I say more....
3. Slavery is a set of acts inherently directed toward the deprivation of fundamental human rights. Although forced labor and racism have often been associated with slavery, the essential moral nature of slavery is the deprivation of fundamental human rights. Any person who is deprived of his or her fundamental human rights is essentially reduced to slavery; such a person is being treated as if he or she is not a human person, but an object, a piece of property, a thing and not a person. (See my book, The Catechism of Catholic Ethics, chapter 21: Slavery, for more on the proper moral definition of slavery.)
This next assertion is neither rhetorical, nor an exaggeration. A set of laws that seeks to deprive illegal immigrants of work, home, medical care, education, and assistance when in great need, thereby seeks to reduce those illegal immigrants to slavery. It is literally a form of slavery to deprive any person or group of persons of fundamental human rights, such as work, home, health care, education, etc.
The set of laws being proposed and in some cases enacted, in various U.S. states, depriving illegal immigrants of these fundamental human rights are essentially an unwitting attempt to reinstitute slavery in the United States of America.
All persons of good will have a grave moral duty to oppose all such laws.
The only moral response
It would be a grave sin to deport 10 million illegal immigrants, or to punish them with incarceration, or to deprive them of fundamental human rights. Therefore, the only recourse that remains is to give them citizenship.
Now a nation has a responsibility to govern its borders. The U.S. has been and continues to be seriously negligent in that responsibility. Our nation does not have an unlimited number of jobs to offer an unlimited number of illegal immigrants (whether they are given citizenship or not). If more and more persons immigrate to the U.S., eventually there will not be sufficient jobs for them, and they will be reduced to severe poverty. The result would be slums, disease, crime, and much harm to those individuals and to society as a whole. Therefore, the U.S. cannot give citizenship to an unlimited number of illegal immigrants. We have a moral responsibility, not only to treat the current set of illegal immigrants as fellow human beings with fundamental human rights, but also to limit the number of illegal immigrants so as to avoid grave harm.
In addition to giving the current set of illegal immigrants citizenship, we should also make every reasonable effort to seal our borders to illegal immigration, so that the number of illegal immigrants does not increase to the point where grave harm occurs to many persons.
Ronald L. Conte Jr.
Roman Catholic theologian and Bible translator
For an in-depth explanation of the basic principles of Catholic moral theology
and their application, see my book: The Catechism of Catholic Ethics