On May 4, 2017, the European Commission (EC) approved and made public:

1. Its recommendation for a Council Decision “authorising the Commission to open negotiations on an agreement with the United Kingdom of Great Britain and Northern Ireland setting out the arrangements for its withdrawal from the European Union”. This text, once approved by the European Council (one Minister per Member State), will become the official and legal appointment of the EC to act as the single “Union Negotiator” with the UK regarding its withdrawal from the EU and (often forgotten) from the European Atomic Energy Community or EURATOM. 
2. An Annex to be approved with that Decision which includes the detailed and specific Directives for that negotiation. This précises sets forth in legal terms the negotiating objectives in several areas for the first phase of the negotiations including: the rights of EU citizens in the UK; financial settlement between the UK and the EU; continued cooperation in certain areas and fora; and a new dispute settlement mechanism. In some cases these can be read as “red lines”, while in others it just identifies the topics to be discussed (some of them have been little discussed in the media).

Only when “sufficient progress” has been achieved on this negotiation, as assessed by the European Council (27 Heads of State/Government), will the Union Negotiator receive new sets of negotiation directives to proceed with the second phase on the future relationship between the UK and the EU including some kind of Trade Agreement and the transitional arrangements or bridges towards that future.

BREXIT is and will remain a very political matter indeed. But it cannot be reduced to that. These documents are the very first that initiate the move from political discussions and debate, and statements to the media, into legal work on legal matters with legal consequences.