[3][4] The changes were intended to take effect following a vote for "Remain" in the UK's in-out referendum in June 2016, at which point suitable legislative proposals would be presented by the European Commission.

Due to the outcome of the referendum in which the electorate voted by 51.9% to 48.1% to leave the bloc, the changes were never implemented and subsequently the United Kingdom withdrew from the European Union in January 2020.

The changes were legally binding insomuch as the intentions and statements made by the EU leaders were enshrined in an international treaty.

On 23 June 2016, the United Kingdom, on a national turnout of 72%, voted by 51.9% to 48.1% to leave the European Union and indirectly reject the terms of the new agreement.

The result received a variety of different reactions internationally and began the process of leaving by invoking Article 50 of the Treaty on European Union on 29 March 2017; after three extensions to the Article 50 process on 31 January 2020 at 23:00 GMT in accordance with the result of the referendum, the United Kingdom became the first EU member state to formally leave the bloc, ending 47 years of membership.

The so-called "emergency brake mechanism" would have allowed member countries to limit access to in-work benefits for new EU immigrants.

Cameron backed the "red card" as a means to support the EU's principle of subsidiarity, which he believed was not fully realised.

[17] Once a citizen lives in another EU country the threshold of reason for the local government to remove them becomes progressively higher.

The consensus from the EU leadership is that the planned changes would have given nations more power to deport criminals and prevent their return[18] but not necessarily restrict movement for other reasons.

The deal would have made no changes to the principle that child benefit should be paid to citizens no matter where their children reside.

[22] The deal explicitly said that the presence of the "ever closer union" phrase in the treaties does not of itself grant the EU any specific competences or powers.

[23] The EU deal attempted to reassure non-Eurozone countries including the UK, that decisions would not be made favouring Eurozone members over them.