To explain the correct libertarian approach to immigration, a thought-experiment posits a minimal-state libertarian UK and then the introduction of several relevant anti-libertarian policies with their increasingly disastrous effects. It is argued that the reverse of these imagined policies, as far as is politically possible, must be the correct way forward. This framing is intended to counter the tendency for many articles to misapply libertarian principles to the current messy situation on the mistaken assumption that a state need only stop interfering without rectifying or adjusting for its previous interferences. The relevant parts of various open-border texts are then criticised in light of this and for other errors, in particular for overlooking the likely huge scale of immigration as indicated by Gallup surveys. Additional criticisms are addressed in footnotes throughout. The conclusion outlines three broad options on immigration and suggests that directionally-libertarian policies are both more libertarian and practical than having states open their borders. The readers that might be interested in this subject matter include those engaging in libertarian philosophy, economics, and political theory.