Earlier quoted context omitted.
If they are German citizens, then the German constitution prevents the state from extraditing them (to a non-EU country). https://www.gesetze-im-internet.de/gg/art_16.html
It's strange to me that many countries sign "bilateral" extradition treaties with Germany or other countries with similar policies such as Brazil.
Article 7
EXTRADITION OF NATIONALS
(1) Neither of the Contracting Parties shall be bound to extradite its own nationals. The competent executive authority of the Requested State, however, shall have the power to grant the extradition of its own nationals if, in its discretion, this is deemed proper to do and provided the law of the Requested State does not so preclude.
In fact, Germany has quite a few outstanding arrest warrants against US citizens, too: https://www.theguardian.com/world/2007/jan/31/usa.germany