The withdrawal of the United Kingdom (UK) from the European Union (EU) had the immediate impact of drawing an external border of the EU on the island of Ireland. With this, two issues related to Northern Ireland came into sharp focus, both of which related to the absence of a physical border, along the border, on the island of Ireland. Firstly, there was the movement of British and Irish citizens within the UK and Ireland, within what is known as the Common Travel (CTA), ensuring, amongst other things, no physical restrictions on the movement of persons on the island of Ireland, amongst other related matters. Secondly, but equally as important, was the issue of a potential border having to be constructed on the island of Ireland between Ireland and Northern Ireland, in the name of preserving the integrity of the EU customs union and the EU internal market. This would have been, because, if Brexit was to mean Brexit, Northern Ireland would no longer be a part of such arrangements, and physical infrastructure, along the legal border, as an external frontier of the EU, would have to be put in place. Sense prevailed however, and a legal solution was found between the EU and the UK to ensure nothing of such a drastic nature occurred. The EU-UK Withdrawal Agreement (WA) that entered into force in February 2020 sealed the fate of Northern Ireland as regards the legal regime governing the absence of a physical border, along the border, between Northern Ireland and Ireland. The WA contained a specific Protocol on Ireland/Northern Ireland (NI Protocol or NIP), which claimed to have the magic formula to ensure the pursued objective. The provisions of the NI Protocol, which is the focus of this chapter, makes up the substantial bulk of the applicable law that governs the special place of Northern Ireland within the EU legal order, for the near future. As a legal text, the NI Protocol is intricate and technical, and not designed to be read by a layman. What the NI Protocol does and does not do has been grossly misconstrued amongst various forms of commentary from political actors and the media alike. Accordingly, this chapter will focus solely on the legal aspects of the NI Protocol, and put it in appropriate legal context. With this in mind, clarification is necessary from the outset. The issues concerning Northern Ireland and EU law are numerous, and this chapter is not to serve as an endlessly exhaustive answer to the full range of legal issues arising from Brexit to Northern Ireland, and nor analyzing all the nuances of the NI Protocol. Nor does this chapter see every eventuality with regard to the matters that it does analyze. Rather, its aim is to position Brexit, and determine the legal aspects of the process and result of the NI Protocol, with the effect that it has had on Northern Ireland, with principle focus on the EU customs union, the free movement of goods, and the enforcement mechanisms. The analysis will not focus, unless otherwise stated, on prior drafts of the parties, or the so-called ‘backstop’ that was initially floated as a solution. Instead, the chapter will focus on the WA and NI Protocol that was ratified by the parties, which is currently in force. The chapter is structured as follows Section 2 examines the initial features of the WA and NI Protocol, taking into account the situation of Northern Ireland, and how its status ran into difficulties as regards the EU customs union. Section 3 analyzed the intricate position of the NI Protocol as regards trade in goods in the form of how the EU customs area is extended to Northern Ireland, and the implications this has on different types of trade in goods with Northern Ireland, as well as the type of regulatory alignment envisaged by the NI Protocol. Section 4 scrutinizes implementation, supervision, and enforcement mechanisms that are foreseen in the NI Protocol, and Section 5 looks at how the NI Protocol can eventually be replaced, or alternatively, seeing it being removed following a procedure involving the political establishment in Northern Ireland. Section 6 analyses the initial implementation of the NI Protocol, whilst Section 7, conclusively, draws some remarks about the future of Northern Ireland and the EU legal order.