Denmark will hold a referendum on December 3 on whether to keep its opt - out to the EU’s justice and home affairs rules. In order to stay on as a member of the European police agency Europol, the country must relinquish the exemption it negotiated after Danes rejected the Maastricht Treaty in 1992, AFP reported. The referendum, which was to be held in 2016, was moved forward, so voters would not be influenced by Britain’s referendum on EU membership. Prime Minister Lars Lokke Rasmussen said that continued Danish participation in the Europol cooperation is central to the issue. Danes adopted the Maastricht Treaty in 1993 after obtaining four opt-outs: the euro, joint defense, judicial cooperation and European citizenship.