Directive 2010/64 on the right to interpretation and translation in criminal proceedings (you can call up a bilingual version here too). The relevant bit is recital 30:
Safeguarding the fairness of the proceedings requires that essential documents, or at least the relevant passages of such documents, be translated for the benefit of suspected or accused persons in accordance with this Directive.
Zur Gewährleistung eines fairen Verfahrens ist es erforderlich, dass wesentliche Unterlagen oder zumindest die maßgeblichen Passagen solcher Unterlagen für die verdächtigen oder beschuldigten Personen gemäß dieser Richtlinie übersetzt werden.
A Dutch national, Frank Sleutjes, was charged with leaving the scene of an accident and served the Strafbefehl (order of summary punishment) in German – only the details on how to appeal were translated. The Düren local court did not translate the order itself – normal practice nowadays. The European court finds that the Strafbefehl is an essential document.
I last discussed the subject here (the language of the court is German). We used to translate these all the time and presumably local courts will now be obliged to have them translated again.
There is not (yet) an English translation of the decision online, but there is an English translation of the Advocate General’s opinion. I see they translate Strafbefehl as penal order. I am not convinced by Tagessätze as daily penalties. More on the English perhaps later.
There is an amusing exchange in the comments on lawblog.