From the time given, its 2 mins after takeoff from EDDF, therefore on the SID, so it looks like a noise issue. They have quoted paragraph 58 (1)(10) of the Luftverkehrsgesetz (German Air Traffic Act) - which I found
here (which subrefers to
Section 32,
32b, and
32c); in connection with paragraph 44 (1) of Luftverkehrs-Ordnung (German Air Traffic Regulation)
here. Chrome gave decent translations.
Although legislation is quite wide-ranging, it pretty much fits that it's noise related, which is quite baffling as I'm pretty sure we were on the SID. How on earth am I supposed to defend myself? Noise related offences are fines on the PIC for up to €50,000. This is insane!