There is lively debate on the question if states have legitimate authority to enforce the
exclusion of (would-be) immigrants. Against common belief, I argue that even non-
cosmopolitan liberals have strong reason to be sceptical of much contemporary border
authority. To do so, I first establish that for liberals, broadly defined, a state can only hold
legitimate authority over persons whose moral equality it is not engaged in undermining.
I then reconstruct empirical cases from the sphere of international relations in which
what I call ‘colonial norms’ continue to play significant structuring roles. I argue that
it is sometimes only by unveiling these colonial norms and the roles they play that we
can understand how some states today culpably contribute to undermining the moral
equality of persons over whom they will come to claim immigration-related authority.
I thus contend that paying attention to colonial norms distinctly enables us to reveal a
set of instances in which all liberals should agree that states forfeit legitimate authority
over would-be immigrants.