Concerns about adverse impacts on the EU in the event UK lowers environmental and social standards in order to gain commercial advantages surfaced only after negotiations on the Withdrawal Agreement between the EU 27 and the UK had completed.
The Northern Ireland Protocol, the magic piece of the puzzle meant to prevent a hard border with the EU, whilst also allowing the UK to restore its borders, contains significant rules relating to a level playing field. They have the potential to be applied for a long-time to come, even if unwanted. Essentially, the backstop requires Northern Ireland to follow the EU’s internal market rules, thus most environmental and health standards concerning industrial production. These include for example the regularly updated emission limit values under the Industrial Emissions Directive or the restriction of chemicals under the REACH regulation. They remain enforceable for Northern Ireland, but not for Great Britain. This means the UK could start to diverge from EU standards for England, Wales and Scotland.
Environmental quality standards, such as for water, air and nature protection, are not covered by the Protocol, except for a “non-regression clause”, which freezes protection levels as soon as the protocol enters into force. Different procedures, such as a joint committee, are provided in the draft Withdrawal Agreement, to put meat onto the bones for enforcement, but are challenged by environmental NGOs (see Guardian article).
Days before the Article 50 European Council of 25 November 2018, Denmark, France, Germany, Italy and the Netherlands demanded stronger level playing field requirements. These calls did not change the text of the Withdrawal Agreement, but were eventually accommodated in the Political Declaration for a future relationship, as well as in a separate statement by the EU27 leaders.
The Guardian on NGO critics on Withdrawal Agreement
Statement by EU27 leaders (25 November 2018)