Thames Valley Police has accepted that search warrants used to raid Andrew Mountbatten-Windsor's homes following his arrest in February were unlawful.
The High Court was told that the former prince and Police had agreed the warrants were unlawful.
However, items seized during the searches remain with Police, with another hearing expected in 2027 to decide whether they can be used as evidence.
Mountbatten-Windsor was arrested on 19th February on suspicion of misconduct in public office and denies any wrongdoing.
High Court Judge Mr Justice Hilliard says the unlawful warrants do not mean the criminal investigation must end.
Police investigations are continuing.
