I am a lawyer specializing in criminal cases, and I guarantee the authenticity and legality of my answers. According to the law, only guardians and close relatives, including parents, children, spouses and siblings of suspects, can entrust lawyers for suspects. Ex-wife has no legal status.
Attachment: Paragraph 3 of Article 33 of the Criminal Procedure Law stipulates that if a criminal suspect or defendant is in custody, his guardian or near relative may also entrust a defender.
In other words, you have no right to entrust a lawyer for your ex-husband.