Can NSD be used against a lawyer?

I read that the results of undisclosed investigative actions, obtained by interfering with private communication, cannot be used in disciplinary proceedings against lawyers. But if, for example, an investigator or prosecutor gives written permission to use such materials, can this data still be grounds for holding a lawyer accountable? It is not entirely clear to me whether this is really prohibited by law, or if there is still some loophole for such use.