Anthony Randazzo, bishop of Broken Bay, near Sydney, will be the first Australian to lead a Vatican office since the late Cardinal George Pell was the Church's finance czar from 2014 to 2019.
The Australian church lawyer was on Wednesday conferred with the title of archbishop and named prefect of the Dicastery for Legislative Texts, one of the most important positions at the Vatican.
The office is responsible for writing and interpreting the Catholic Church's in-house canon law, and also provides legal advice on other matters, including for the Vatican City State.
Randazzo, 59, is relatively young to lead a Vatican office.
He could serve in the role, responsible for organising and interpreting the Church's system of laws, for a decade or more.
His predecessor was Italian Archbishop Filippo Iannone, who Leo appointed in September to lead the Vatican office responsible for selecting Catholic bishops around the world.
Before being named a bishop, Randazzo studied canon law at the Jesuit Pontifical Gregorian University and worked for five years in the Vatican's Congregation for the Doctrine of the Faith.
Among other things, the office processes clergy sexual abuse cases worldwide.
As a young bishop working at the Congregation's office, Randazzo was in a position to deal with the fallout of the abuse crisis, including during the period in which Australia's Royal Commission conducted an in-depth investigation into decades of cases of priests raping children and bishops covering it up.
The Pope is also a canon lawyer, and the appointment of an Anglophone legal expert familiar with the grave shortcomings of the way the church mishandled the abuse crisis is perhaps telling.
While Leo has given no indication that he intends to make changes, canon lawyers, victims and outside experts have faulted the canonical system and the way it has been used as part of the problem.
Closer to home, the recent Vatican financial trial involving a cardinal has also revealed the limitations of the city state's outdated criminal and procedural codes.
In a statement on his Facebook page on Wednesday, Randazzo said he was grateful for Leo's trust.
He said he would remain in Australia for the next three months before moving to Rome.
with AP
