In the case of extradition, the nationality of the person concerned is particularly decisive. Germany, for example, does not extradite German citizens to third countries. Since Brexit, the United Kingdom has been a third country. According to the German Federal Ministry of Justice, German citizens may only be extradited to other EU states following Article 16 of the German Basic Law (GG) and, therefore, no longer to the United Kingdom.
However, suspected offenders who are nationals of a third country may continue to be extradited to the United Kingdom under the extradition provisions now in force. Concerning EU citizens, the same provisions apply as are generally applicable to the extradition of EU citizens to third countries. More information on the extradition of EU citizens can be found here.
Germany is not the only country to take this step and no longer extradite its citizens to the UK. Other countries have already told the European Commission that continuing the current arrangement after Brexit would violate their respective constitutions. In general, countries are reluctant to extradite their nationals, as the extradition case of Carlos Ghosn shows. Other EU countries have national laws similar to Germany that prevent the extradition of their citizens to non-EU member states.
In response, the UK stated that it expected the member states concerned to conduct the respective criminal proceedings themselves.
German law only prevents the state from extraditing its nationals to third countries but not from conducting the proceedings itself. Accordingly, German citizens could expect criminal proceedings in Germany instead of extradition to the United Kingdom.