2015–2016 United Kingdom renegotiation of European Union membership

The so-called "emergency brake mechanism" would allow member countries to limit access to in-work benefits for new EU immigrants. This would have needed the agreement of the European Parliament and the UK would need the agreement a majority of other governments through approval in the Foreign Affairs Council (of Member States).[6]

Under current rules, other EU citizens can ultimately claim most of the same benefits as a UK national. Some of the benefits are subject to a test on "Right to Reside"[7] for which EU citizens will almost certainly qualify. Most benefits also require Habitual Residence[8] which means that for the most EU Citizens they will have to wait three months before claiming Jobseeker's Allowance, Child benefit or Child tax credit.[9][10]

Under the emergency brake (which needs first to be established in EU law),[6] the European Council (of national Heads of Government) could authorise a country that is experiencing migrant flows of "exceptional magnitude" to restrict benefits for new migrants for four years (with migrants starting with no entitlement then gradually gaining rights to benefits).[6] These restrictions could be kept in place for up to seven years but could be used only once.[6][11] (In this case "established in EU law" means the EU Commission proposing draft legislation for approval by the European Parliament). Subsequently, member states [but specifically the UK] could request and apply it to migrants reasonably quickly, with the Commission already expressing that they believe the UK would be justified in doing so.[12]

The "red card" would have allowed a member of the Council of the European Union with the support of 15 other members to return a recommendation to the European Parliament for further changes. This is not a veto as EU politicians could still go ahead if they judge that they have addressed the concerns raised by the "red card",[13] which is named after the penalty card used in football.

Cameron backed the "red card" as a means to support the EU's principle of subsidiarity, which he believes is not fully realised.[14] In this way the "red card" is intended for groups of countries to block or reform EU rules where they think it is their job, rather than that of the EU, to make laws on a particular subject. The "red card" will join the existing "yellow card" (which has been triggered twice) and the "orange card" (which has never been used).[15] The use of the "red card" will require backing of 55% of governments at the Council, which is slightly less than is required to approve directives – which is 55% of all countries and votes representing 65% of the EU's population.[16]

Free movement of people is an important tenet of the European Union and enshrined in primary law in treaties.[17] The EU deal subtly changes the free movement rules to make it easier for countries to deport migrants from other EU countries. This is achieved by "beefing up" the exceptions to the general rule that EU citizens can live and work where they choose in the EU.[18]

National governments have a carefully restricted ability to restrict the free movement of people about the EU.[19] Once a citizen lives in another EU country the threshold of reason for the local government to remove them becomes progressively higher.[18] The changes planned in the EU-deal are subtle changes of wording to permit governments to take in to account where migrants' behaviour is "likely" to represent a threat, rather than that it "does",[20] and allows government to take in to more account a person's past behaviour rather than just their present behaviour.

Until they are implemented and tested in European Law through the EU's European Court of Justice and, possibly, in the (non-EU) European Court of Human Rights, it will be hard to quantify the impact of these changes. The consensus from the EU leadership is that they will give nations more power to deport criminals and prevent their return[21] but not necessarily restrict movement for other reasons.

The deal makes no changes to the principle that child benefit should be paid to citizens no matter where their children reside. However following the deal governments will be able to adjust the payment they make to reflect the standard of living in the country the child lives and the amount of child benefit that would normally be paid in that country.[22]

Although many people have questioned the idea of paying child benefit for children living in other countries,[23] it is a logical consequence of the EU's principal of non-discrimination – as migrants are more likely to have children in another country and would therefore be discriminated against by restricting those benefits.[22] Once the changes to law were passed to reflect this agreed change it would be up to the Court of Justice to clarify if it is legal or there are any unintended consequences if it was subsequently challenged.

In the EU deal there was a statement specifically exempting the UK from "ever closer union". The precise phrasing of the aspiration, which was in the preamble of the EU's founding treaty[24] and every treaty since is "ever closer union of the peoples [of Europe]". The phrase has symbolic political status but it has little or no legal effect in any of the treaties and thus UK's exemption from it is equally symbolic.[25] The deal is explicit in saying that the presence of the "ever closer union" phrase in the treaties does not of itself grant the EU any specific competences or powers.[26]

The EU deal attempts to reassure non-Eurozone countries including the UK, that decisions will not be made favouring Eurozone members over them. There will now be a system for non-Eurozone members to object to rules being passed that might harm them but it will not give them a legal opt-out. However EU law already bans discrimination so this is merely an additional protection.[27]

Along with Denmark the UK has an opt-out to the 1992 Maastricht Treaty which means they are not technically obliged to join the Euro.

Prior to this EU deal there was concern[28] that Eurozone members may discuss matters of the EU and single market separate to the wider membership and therefore come up with a deal they could theoretically impose on non-Eurozone countries. In the Council, Eurozone members would have sufficient majority to pass directives if they wished, although those proposals would need to be proposed and drafter by the Commission first and also approved by the European Parliament.

In addition to specifically banning such discrimination it also contains a statement of intent that any measures for "economic and monetary union" will be voluntary for non-Eurozone countries, and that those countries will not stand in the way of such measures for those in the Eurozone. For example, non-Eurozone countries will not be required to contribute to bailouts for Eurozone countries.[29]

The European Parliament intends[30] to bring forward legislation to change EU law to limit the ability of a non-EU national to gain the right to live and work anywhere in the EU (including the UK) by becoming the spouse of an EU citizen. There has been some back-and-forth on the matter in the European Court of Justice with existing laws being inconclusive.[31] This change to the law, if approved, should clarify the matter.[32] The changes to the law could still be challenged in both the EU Court of Justice and the Court of Human Rights (which is not an EU institution).

This change in law is not intended to deal with deliberate abuses of the immigration policy (sham marriages) for which existing tools exist.[33]

The EU deal would have been international law, as it was made by European heads of government acting outside the structure of the EU. The UK intended to register it as such.[34] This would have meant that statements and intentions made within it cannot be challenged by the Court of Justice. However, certain aspects of it would need treaty change within the EU[35] and certain elements would need legislation to become part of EU law. The Commission had already indicated its intention to bring the legislative requirements to the EU Council and Parliament for passage.[36] Cameron stated that he had lodged the documents with the United Nations. The UK Independence Party leader and MEP Nigel Farage criticised the deal for not being made legally binding prior to the referendum and stated that in regard to lodging a deal with the EU with the UN, Farage stated "you may as well lodge an old pair of socks because it's completely meaningless".[37]

On 27 June 2016, David Cameron said in his statement to the House of Commons on the result of the referendum to "Leave the European Union": "The deal we negotiated at the European Council in February will now be discarded and a new negotiation to leave the EU will begin under a new Prime Minister."[38]

• European Union law