The governments of the world are limited in their jurisdiction — limited in space, time, and matter, both in content and in person. A government is the representative of a whole people. There are many people, with different languages, who may commodiously bind themselves together as one people, by virtue of their situation, tongue, and culture. The formation of governments, to grant sovereignty amongst men, must be limited by the aforesaid factors. Diversity implies limitation. The formation of laws not common is a contradiction in terms. The laws of one people hold only over those people. For example, the communication of laws is necessary to their enforcement, hence only those to whom it may be communicated in a common tongue are bound.
It is immoral, and illegal (that is, contrary to the institution of law) for a government of limited jurisdiction to form laws prohibiting or criminalizing either immigration or emigration. Governments have, in time of peace, no authority to ban or outlaw people seeking to cross or enter their borders.
The proof is this: an immigrant is, prior to immigration, outside the jurisdiction of the government whose land he seeks to enter, whose people he seeks to join (whether civilly, as a member of the community, or officially, as a citizen, or in any other manner); therefore, he is not under the jurisdiction of laws prohibiting him from doing so. And once he crosses the border, he is now under the jurisdiction of that government, and no law can be formed against his having done so. Neither may a government form laws preventing men from leaving their own country, for to leave one jurisdiction is to enter into the sight and sound of another.
These rules apply only to the act and intention itself, not to any adjuncts, accidents, or circumstances of his immigration. One who crosses a border to commit a crime, may yet be punished for his crime, whether he does so in his own person or in that of another.
This rule does not apply in times of war, where the innocent party has a legitimate claim to the territory of the aggressor, either to annex, liberate, or occupy. The purpose of war is to decide between claims that can in no way be settled through civil process, and by declaration of war each country establishes a legitimate claim to the land of the other, to prohibit entry from one to the other, for the purpose of defense.
Governments may indeed regulate immigration, but a power to regulate is a prohibition of the destruction of the thing to be regulated. To regulate means to make regular, and a thing that is destroyed is not made regular, because it is not at all. Governments have a civil authority to ensure that immigration takes place in a peaceable, orderly manner, to advise immigrants of the laws and customs of the land to which they have come, and to steady the flow of immigrants to various places, in order to avoid an excessive flux in the population.
This is not the same as picking and choosing who shall come and who shall not — such holier-than-thou thinking is forbidden to governments; nor is it the same as refusing access because some may use that access for illegal purposes; nor is it the same as discouraging people to come, or reducing the amount of immigration that would naturally occur. These must all be dismissed with prejudice, because a government of limited jurisdiction has no authority over those beyond its borders.
The governments of this world have no authority to forbid men to enter their lands, or to leave them; their jurisdiction is limited to their own borders; and their duty is to govern those within their lands, and not meddle in the affairs of others. There is no such thing as “illegal immigration.” Immigration is inherently legal, and belongs to the constitution of limited government.