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

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.

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.