The Withdrawal Agreement (WA) was signed on behalf of the UK by Boris Johnson shortly after his party won the 2019 general election. The Withdrawal Agreement - including the NIP - bind the UK in international law.
Some negotiations between the UK and the EU took place and here is a summary up to the end of October 2021 - Four non-papers and a command paper - Queen's Policy Engagement (qub.ac.uk).
Furthermore, there has been much noise from within government about the possibility of "triggering" Article 16 of the NIP - Law and Lawyers: Article 16 of the Northern Ireland Protocol (obiterj.blogspot.com). However, the government has now chosen not to follow that route.
Instead,the government has put a Northern Ireland Protocol Bill to the House of Commons and has backed up the Bill by a published legal position -
This follows on from a statement by the Foreign and Commonwealth Secretary (Liz Truss MP) to the House of Commons (17 May 2022) -
Explanatory notes to the Bill have also been published - Notes - Northern Ireland Protocol Bill
The Bill starts with the following curious Clause -
The clause is curious because it appears to merely set out what the Act seeks to do but does not, in itself, seem to make any new law. It reads more like a lengthy preamble. Of course, the clause makes it very plain that Ministers will be granted extensive powers in relation to the protocol's effect in the UK.
Needless to say, the government's actions have already been the subject of considerable comment in the media and elsewhere and some links appear below.
The immediate appearance is that of a government willing to ride roughshod over an international agreement entered into willingly by Prime Minister Johnson in December 2019. The consequences of that for UK-EU relations may be very profound and the UK is showing, to the world at large, a worrying willingness to breach its international obligations.
House of Commons Library - explainer:
Addendum 23 June 2022 -
Additional analysis / commentary may be seen at
Addendum 28 June 2022:
The Bill received its 2nd reading in the House of Commons by a vote of 295 to 221 - see Hansard - Northern Ireland Protocol Bill - Hansard - UK Parliament
Addendum 29 June 2022:
Addendum 3 July 2022:
Addendum 5 July 2022: