For Helmut Siekmann elimination of cash payments would hardly be compatible with Basic Law ("Wiwo.de")
According to Siekmann, the elimination of the 500 euro bill would not be illegal at first sight. However, prohibiting payments of more than 5000 euro by cash would be legally dubious under European and constitutional law, Siekmann said.
Wiwo.de: "Abschaffung wäre kaum mit dem Grundgesetz zu vereinbaren"