Libertarians should be skeptical of both state-restricted and state-engineered migration, since both distort natural market processes. In a libertarian society, movement is not an entitlement but emerges from the interplay of property rights and market forces. Thus, while open borders remove government aggression against migrants, they do not inherently produce a truly market-mediated pattern of movement.
Some also contend that open borders create forced association by compelling taxpayers to support and interact with people involuntarily. They question whether coercively funded systems should be made universally accessible. Another concern is that rapid influxes of immigrants (as seen in parts of Europe and during the Biden administration) can destabilize communities, strain infrastructure, and hinder integration. These libertarians suggest that importing large numbers from regions less friendly to liberty may have significant consequences, while still acknowledging that immigrants are never a monolith and that the desire for all immigrants is to integrate well and flourish in their new society.
To be clear, these libertarians support free trade. Many are anarchists who want to abolish the state and borders entirely, but they stress that the order of transitional steps taken to dismantle state powers shouldn't be ignored. Proposed alternatives include private sponsorship or invitee systems, "Ellis Island" style entry points, decentralizing authority to states, or limiting access to public services until those systems can be privatized or decentralized.
This question is from Faith Seeking Freedom: Updated & Expanded, available in paperback, PDF, and Kindle.