While practising law in Venice, Arbia passed a public competitive examination to become a judge and prosecutor in Italy, positions which she held until 1999.
During that time, Arbia was a fervent advocate of human rights, a subject which she taught at the LUISS University in Rome and at the Police Academy.
On several occasions, she was appointed to represent the Italian Ministry of Justice in various international programmes on topics such as "Concerted European initiatives and Italian legislation to combat human trafficking and sexual exploitation of children" and "Victims of crimes in the European Union".
As Chief of Prosecutions, she led all prosecutions'teams and the prosecution in some of the most significant cases before the ICTR: Arbia participated in the drafting of the Rome Statute of the International Criminal Court as a member of the Italian delegation at the diplomatic conference held in Rome in 1998.
Her election as Registrar of the International Criminal Court on 28 February 2008 was a logical progression from her career at the ICTR.