After the Danish no-vote in the Maastricht referendum, in October 1992 seven out of eight of parties of the Folketing agreed on the so-called "National Compromise". The agreement was the starting point of the Danish Government at the negotiations with the other EU-memberstates.
All four Danish opt-outs are laid down in the Edinburgh Agreement and supplemented by a special Protocol attached to the Treaty of Amsterdam. Denmark’s opt-outs cannot be changed without Danish consent and will be maintained for as long as Denmark wishes. In November 2007, the Danish Government announced its ambition to put the opt-outs to a referendum in the course of its present four year term. The ambition has been confirmed by the Danish Prime Minister on several occasions but a referendum date is yet to be announced.
Folketinget, the Danish Parliament, commissioned the Danish Institute for International Studies (DIIS) to produce a report on the consequences of the Danish opt-outs in the context of subsequent developments in European co-operation with a particular focus on the past decade. The report was published by DIIS on 30 June 2008 and can be downloaded here .
The opt-outs are maintained in the Treaty of Lisbon, ratified by Danish Parliament in April 2008. Yet the Treaty has opened the possibility that Denmark’s opt-out regarding the cooperation on justice and home affairs in the EU can be changed, subject to approval by referendum. If approved, Denmark will be able to co-operate in justice and home affairs on a case-by-case basis.