Prime Minister Boris Johnson wins the British general election. It is therefore likely that the Brexit deal will soon be adopted. If the British Parliament approves the agreement, the European Parliament can vote on it in January. Both the draft withdrawal agreement and the political declaration have a potentially considerable impact on the British Constitution. Some of the constitutional issues that are likely to arise in a draft law on the implementation of the withdrawal agreement are: free movement will continue until the end of the transition period (or the transposition period) and EU and UK nationals will be able to move to the UK or Member States, as currently permitted by EU legislation. EU citizens living in their host country before the end of the transition have a permanent right of residence under the withdrawal agreement due to certain requirements. Under the agreement, the UK and EU-27 have discretion under which EU or UK nationals must apply for new resident status. This is the third time the British Parliament has rejected the agreement. The UK has until 12 April 2019 to decide how to proceed: the UK Parliament must proceed with two approval procedures before the UK can ratify the withdrawal agreement. Both the EU Law (Withdrawal Act 2018) and the Constitutional Reform Act 2010 and the Governance Act (CRAG) are obstacles to the UK`s ability to ratify the negotiated agreement.
The Withdrawal Act also provides for parliamentary procedure in the event of a rejection of an agreement by the House of Commons or if a negotiated agreement is ever reached. On 15 January 2019, the House of Commons voted with 230 votes against the Brexit withdrawal agreement the largest vote against the British government in history.  The government may survived a vote of confidence the next day.  On March 12, 2019, the House of Commons voted 149 votes against the agreement, the fourth-biggest defeat of the government in the history of the House of Commons.  A third vote on the Brexit withdrawal agreement, widely expected on 19 March 2019, was rejected by the House of Commons spokesman on 18 March 2019, on the basis of a parliamentary convention of 2 April 1604, which prevented British governments from forcing the House of Commons to vote several times on a subject already voted on by the House of Commons.    An abbreviated version of the withdrawal agreement, in which the annex political statement had been withdrawn, consisted of the test of “substantial amendments,” so that a third vote was held on 29 March 2019, but was rejected by 58 votes.  The political declaration provides that the EU-UK agreement on future relations will essentially be an economic and security partnership. In accordance with the political declaration, the 27 EU Member States agreed on 25 February 2020 on the negotiating mandate of the European Commission, which is negotiating on behalf of the Member States on future relations between the EU and the UNITED Kingdom.
On this basis, the EU`s chief negotiator, Michel Barnier, presented in mid-March a draft comprehensive agreement on the new partnership with the UK, to which other elements were added. You can find this and the others on the UK Task Force`s website. The NI protocol, known as “backstop,” is supposed to be temporary and applies unless it is replaced by a future relationship agreement that the parties will attempt to reach by December 31, 2020. The protocol provides that the common travel area and North-South cooperation will continue to a large extent as they do today, as well as the internal electricity market (so that some EU legislation on wholesale electricity markets will continue to apply).