Today, the Danish government announced the date for the referendum on the Danish opt-out on Justice and Home Affairs. The decision to hold a referendum on 3 December 2015 follows a political agreement between the government, the Conservative Party (Konservative Folkeparti), the Social Democrats, the Social Liberals (Radikale Venstre), and the Socialist People’s Party (Socialistisk Folkeparti) from 10 December 2014. If the referendum turns out positive, Denmark will change its opt-out on Justice and Home Affairs into an opt-in (see Annex to Protocol 22 to the Lisbon Treaty). The opt-in model will allow Denmark to choose to opt-in to existing JHA-legislation, which Denmark is not part of today, and any future legislation in this area.
In a political agreement from 17 March 2015 the parties have carved out the list of legislative files that Denmark will opt-in to if the upcoming referendum turns out positive.
Link to the political agreement.