Switzerland and the EU have been negotiating the possibility of linking their emissions trading systems since 2011. Both the Federal Council and the EU Council of Ministers issued a corresponding negotiating mandate. The technical negotiations were concluded in January 2016 with the initialling of an agreement. The agreement was signed on 23 November 2017 in Berne. Following its approval by the EU and by the Swiss Parliament, it was ratified by Switzerland and the EU in December 2019 and entered into force on 1 January 2020.