EU and the German constitution

According to EU Referendum,

Roman Herzog, former judge and German president between 1994 and 1999 ... says... in the newspaper Welt am Sonntag today, ... "EU policies suffer to an alarming degree from a lack of democracy and a de facto suspension of the separation of powers."

What is more, Herzog has a co-author, the director of the Centre for European Policy (CEP) in Freiburg, who goes by the name of Lueder Gerken. And among their criticisms is that the German parliament was not involved in European Union legislation as required by the German constitution.