The European Commission said it launched the infringement proceeding because the UK has failed to implement the agreement “despite repeated calls” to do so.
The EU said that renegotiating the protocol was “unrealistic” and that changing it unilaterally would be considered a breach of an international agreement, which could result in fines.
“Acting unilaterally is not constructive. Violating international agreements is not acceptable,” Maroš Šefčovič, the European Commission Vice-President, said in a statement.
The agreement was put in place to safeguard the Good Friday Agreement, which helped end years of deadly sectarian violence and which mandates that there should be no hard border between the Republic of Ireland, which is part of the EU, and Northern Ireland, which has left the EU alongside the rest of the UK.
To avoid a hard border, the UK has agreed to keep Northern Ireland within the EU regulatory scheme. That solution, however, created another headache: because the rest of the UK does not fall under EU rules, goods leaving Northern Ireland for the rest of the UK would have to be checked.
Speaking to reporters on Wednesday, Šefčovič, said that aside of launching the legal procedure, the EU was also putting forward some “additional details” on the possible solutions it has suggested earlier.
This is a developing story.