The Council of State kept the investigation secret until documents were leaked to Il Fatto Quotidiano last month.
The newspaper published only a summary of the documents but allowed the Washington Post to review them.
Only after that leak prompted a media uproar were two criminal investigations opened against Bellomo.
Italy's High Council of the Judiciary, which oversees the country's judges, also opened a disciplinary investigation into some of Bellomo's aides.
In addition to sitting on the Council of State, Bellomo was the director of Diritto e Scienza, a private school that prepares hundreds of graduate students each year for the state exam to become a judge, and also taught classes there. Bellomo allegedly used his authority to have sex with female students.
That behaviour is not illegal in Italy and would rarely prompt a disciplinary measure. But when students tried to break off their relationships with him, he allegedly intimidated them by detailing their private lives in the school's academic journal, threatening gratuitous legal action and, in one instance, sending the police to a woman's house.
At Diritto e Scienza, students were divided into two groups: regular students, who paid tuition and could live normal lives, and top students, who received scholarships in exchange for signing contracts in which they pledged loyalty to Bellomo himself, took a vow of secrecy and relinquished the freedom to date whom they pleased (any significant others needed to be approved).
They also had to comply with a detail-obsessed dress code that required women to wear miniskirts leaving at least two-thirds of the thighs exposed.
The school taught a bizarre legal doctrine based on Bellomo's belief in the existence of superior humans — "superior agents," who could "exercise strong control over nature". Bellomo argued that the law should be applied differently to them.