Citizenship laws provide us with models of membership. They define the terms on which strangers and natives belong to political communities, allocating both the benefits of membership and the brutalities of exclusion. Recent legal changes in Ireland, restricting the right to citizenship by birth and limiting the rights of migrant families, highlight the vulnerability of children in migrant families and the limits of citizenship status. Many other states have grappled in recent times with the right to citizenship by birth and the entitlements to family life that come with such a claim. In both the UK and Australia the jus soli principle has been significantly restricted. In the US, Canada and elsewhere, while the jus soli principle continues to apply, citizen children born to undocumented migrant parents are subject to de facto deportations, their right to membership of the nation-state ‘postponed’ because of the legal status of their parents. In challenges to deportation proceedings involving such children, the perspective of the child as a bearer of rights is marginalised, with disputes turning largely on the balancing of states' interests in immigration control against the residence claims made by migrant parents.