The 80-year-old faces formal charges including "treasonous espionage, spying out state secrets, attempted treason, and espionage" - according to German media. While an official statement from the prosecutor's office has not yet identified the foreign service he's suspected of working for, Israel has been widely named, also given this past well-documented associations and links.
https://www.zerohedge.com/geopolitical/germanys-former-spy-chief-arrested-biggest-espionage-scandal-century
The associated link, one in this case…
https://www.trtworld.com/article/0f001a4ec77e
Police believe that “Block and her partner, a former television sports presenter, hired an Israeli business intelligence company in 2023 to carry out the abduction,” Haaretz newspaper said.
According to the daily, prosecutors told the court in Hamburg that August Hanning, the former head of Germany’s Federal Intelligence Service, “contacted Perry last year on Block’s behalf and asked him to put together a team to kidnap her children from their father, who claims that staying with their mother puts them in danger.”
Hanning denied any involvement, telling the German newspaper Bild that he “never contacted Perry.”