https://www.independent.co.uk/news/u...-a8564551.html

In UK law, no agreement is sacrosanct, but the GFA has worked well in the past.
If the EU want to "evolve" the agreement to solve the border issue that will have to be approved between those who signed the original agreement or their representatives.

Any amendment or new agreement must be debated and approved by parliament and all parties involved. Arlene was previously against making the GFA so her motives are a little suspect.