See also: morality of violating restrictive immigration laws, law versus legislation, nomenclature for illegal immigrants, and get in line.

Some people favor a liberalized immigration policy and/or guest worker program in the developed world, but believe that before such a policy can be implemented, illegal immigration must be stopped. For instance, in a syndicated column piece titled Immigration and Liberty, George Mason University economist Walter Williams writes:

Here’s Williams’ suggestion in a nutshell. Start strict enforcement of immigration law, as Arizona has begun. Strictly enforce border security. Most importantly, modernize and streamline our cumbersome immigration laws so that people can more easily migrate to our country.

He is also approvingly quoted by Daniel J. Mitchell. Williams wrote a similar piece here.

Side remarks

• The issue is less central than it appears to be: The majority of opponents of illegal immigration also do not favor liberalized immigration laws. Many opponents of illegal immigration are opposed to low-skilled immigration at large, and some groups are opposed to all immigration. A. Barton Hinkle considers this in a column for Reason Magazine titled Is It the Illegality—or the Immigration? You only have to scratch the debate to see the degree to which legal technicalities are orthogonal to the main issue.
• Many opponents of illegal immigration among the general public are not well-informed about the difficulty of legal immigration: Hence, the constant refrain to get in line.

Counter-arguments

• Morality of violating restrictive immigration laws: Some libertarians, such as Nathanael Smith, have argued that when a law is completely unjust, violating that law is not, in fact, immoral. (Quote from Nathanael Smith’s book below). A similar argument is found in the piece Why Is Immigration Illegal Anyway? by Benjamin Powell and Art Carden (quoted below). Another similar argument is found in the article Are Illegal Immigrants Criminals? Not! by Ken Schoolland for the Future of Freedom Foundation website. Another similar argument is made in the article Human Smuggling is Morally Good by Scott McPherson for the Future of Freedom Foundation website. Vipul Naik considers the parallels between illegal immigration and illegal emigration in the blog post immigration, emigration, and the rule of law.
• Law versus legislation: Some libertarians, such as Donald Boudreaux, have argued that “law” is not the same as “legislation” and that in their day-to-day market and personal interactions, most people don’t care about whether the people they are interacting with are “legal” or “illegal” immigrants. This shows that, as far as practical law is concerned, illegal immigrants are not illegal. (Excerpts below).
• Some versions of the “legal versus illegal” argument lay emphasis on the fact that their own ancestors migrated legally, so why shouldn’t immigrants today do the same? This combines the legal versus illegal distinction with the then versus now distinction. This distinction is dealt with in the article Why Is Immigration Illegal Anyway? by Benjamin Powell and Art Carden (quoted below).
• Some people have considered analogies between immigration restrictions and gun control to point out what they perceive as the absurdity of requiring full compliance with existing immigration law before considering reform.

In his book Principles of a Free Society, Nathanael Smith writes that violating immigration restrictions may be not only morally permissible, but morally good:

The general liberty to use the streets therefore has a basis in natural rights, applies equally to citizens and non-citizens of a state, and cannot be justly restricted by a government except when the streets are used in ways that constitute an objective danger to its citizens’ safety (e.g., drunk-driving, gang-warfare, or the transportation of hostile armies). Illegal immigrants are (at least in some cases) conducting a form of civil disobedience against an unjust law. It is the law, not the immigrant, which is in the wrong, and the law should be changed, rather than the immigrant removed.

Smith, Nathanael. Principles of a Free Society (Kindle Locations 2689-2693). The Locke Institute. Kindle Edition.

In an article titled Why Is Immigration Illegal Anyway? for the Independent Institute, Benjamin Powell and Art Carden write:

The last refuge of the defenders of the new Alabama legislation is to protest that this is not about immigration per se, but about illegal immigration. Perhaps you acknowledge that we are a nation of immigrants but protest that your ancestors came here legally. That dodges the issue. To move to the United States legally in the 19th century and to move to the United States legally in the 21st century are two very different undertakings. We are willing to bet that our ancestors—and yours—would find themselves in the same position as many potential immigrants today: effectively denied entry by layers and layers of red tape.

Defenders of restrictions might insist that the restrictions are still the law, but lots of immoral and unwise things—like slavery and Jim Crow—used to be “the law.” Simply repeating “what part of ‘illegal’ don’t you understand?!” misses the real question: Why does the law make it illegal to migrate here? Immigrants are a boon to our economy and restrictions on immigration seem as immoral as many other past laws. Yes, the “illegal” part of illegal immigration is a problem. Alabama’s legislators are addressing it the wrong way. As our friend Mark LeBar, a philosopher at Ohio University, has put it, illegal immigration is one of very few issues that really has a magic wand solution: Legalize it.

In a blog post titled Are ‘Illegal’ Immigrants Illegal?, Donald Boudreaux, draws on a Hayekian interpretation of “law” and writes:

I concede that many people today are in the United States without Uncle Sam’s formal permission. I disagree, however, that these people are ‘illegal’ or ‘criminal’ in any but the most formal and empty sense of the terms.

Law is not so much what legislatures declare it to be; law, instead, is the complex of norms and expectations that motivate most people in a community. In some states – including, I believe, Georgia, Massachusetts, and Mississippi – the legislative codes still prohibit sexual intercourse between unmarried persons. Suppose you’re a resident of one of these states and you’re called to jury duty. The case is State v. Jones, where the state government is prosecuting Ms. Jones (an adult) for having voluntary sex with her boyfriend (also an adult) in the privacy of their own home. Would you vote to convict Ms. Jones even if both Jones and her boyfriend admit that they are not married to one another but that they routinely have sex with each other in private?

Would you find it compelling if someone argued “Look, I personally have no problem with unmarried adults voluntarily having sex with each other. But the law’s the law! If unmarried adults want to have sex, let them do it legally; let them first get married or move to a state that doesn’t criminalize fornication. Then they can screw each other all they want. But if the law says that sex between unmarried people is illegal, then if we let people get away with breaking this law openly, arrogantly, we risk undermining the rule of law in the United States.”

[…]

And so it is with so-called “illegal immigration.” Although not as universally accepted today throughout America as is consensual sex among unmarried adults, immigration without permission of government is widely enough accepted that we can conclude that it is lawful, despite what is written in the statute books.

Employers hire foreign workers without caring much whether these workers can document that they are in the U.S. with Uncle Sam’s permission. Consumers patronize commercial establishments without caring enough about the official status of these establishments’ workers to cause these consumers to seek out establishments that clearly document that they hire only ‘legal’ workers. And save for a relatively small handful of busybodies – such as the so-called “Minutemen” – we Americans in our private choices and actions do virtually nothing to hinder ‘illegal’ foreigners from living and working and playing in our midst.

A ‘law’ that is overwhelmingly ignored – a ‘law’ aimed not at protecting innocent people from the initiation of force or fraud by others but, rather, at protecting one group of people from the economic competition of another group of people – a ‘law’ that depends for its creation and enforcement upon both ideological and economic interest groups whipping up political passions – any ‘law’ with one or more of these characteristics is not really a law. At best such a ‘law’ is a government command that must be enforced without the active cooperation of the populace and, in many cases, against the revealed wishes of this populace.