The Memorandum of Understanding (MoU) concluded between the UK and Ireland in May 2019 provides one of the few clear legacies of Theresa May’s premiership. The Common Travel Area (CTA) between Ireland, the UK, the Channel Islands, and the Isle of Man provides the basis for domestic immigration and nationality laws which permit Irish citizens to reside in the UK and for them to be treated as “not foreign” in the context of UK domestic laws concerning access to healthcare, employment, social security, political participation, and education. Yet it has long lacked legal definition. The UK and Ireland reciprocate, to a rough extent, these rights for each other’s citizens. The MoU and related developments mark the first steps towards clarifying the CTA’s scope. The rush to conclude this MoU and alter parts of both countries’ domestic law relating to the CTA nonetheless illustrate the fragile state of Ireland–UK relations with Brexit looming. This Article explores whether these reforms will enable people who rely upon the CTA as a foundation of life outside their home country to protect their interests through litigation, and reflects upon the relationship between these arrangements and the protections for EU citizens proposed under the UK–EU Withdrawal Agreement.