The First Amendment to the Constitution outlines a fundamental series of Rights, among which is the Right to Association. That is the Right to choose to engage with any other human being in a common cause - be it a financial transaction or an ideological pursuit. Part of one's association with one's nation involves a voluntary association with the terms and rules of participation in that nation agreeable to existing members. Just to reiterate, but there are three incontrovertible conditions inherent in Association: 1) that it is "of one's own free will" (now where do you think I got that one), 2) that there are rules for which the violation may be dis association and 3) that any application for association is dependent on existing members' approval. Failure to meet ANY of those three qualifications delegitimizes any claim to valid association.

Immigration is an application for association. It is that simple. If the applicant does not apply of their own free will, fails to live by the terms/rules/conditions/laws of the association, or fails to gain the approval of existing association members, their applications may be rejected and membership denied. Existing members who break the terms may be excommunicated/disfellowshipped/disbarred from that association.

To a pointed example:

When Dagny broke through the barrier into the Gulch, was she an illegal immigrant? Yes, and Galt told her so. Her method of entry into the Gulch was not through the approved channels or methods. (She had been invited and rejected the invitation.) And while she was accorded status as a guest during her stay, she was reminded that she had broken the rules and could not stay without agreeing to the rules writ large upon the power plant Galt built there.

Every nation in the world has similar rules which apply to their citizens: rules that trade promises of protection of various degrees in exchange for certain duties such as paying taxes and obeying the laws. Guests are those who are not citizens but who nevertheless apply for a lesser status of protection in exchange for a lesser status of duty (such as paying taxes, etc.), but guests are not (with ambassadorial exception) typically granted immunity from the host country's laws and rules. (Ambassadors and consul staff must register with the host nation for recognition of such status - an association contract in and of itself.)

Illegal immigrants attempt to avoid every part of the duty yet seek to avail themselves of every part of the benefit of the association. They are looters in every respect. To attempt to legitimize any such is in direct contradiction of Objectivist principles.