GDPR allows for this as far as i can tell (IANAL)
> Paragraphs 1 and 2 shall not apply to the extent that processing is necessary:
> ...
> for the establishment, exercise or defence of legal claims.
> Paragraphs 1 and 2 shall not apply to the extent that processing is necessary:
> ...
> for the establishment, exercise or defence of legal claims.
‘Processor’ means a natural or legal person, public authority, agency or other body which processes personal data on behalf of the controller.