Mokbel pleaded guilty to three counts of drug trafficking and in 2012 was sentenced to 30 years' prison, as a result of operations dubbed Quills, Orbital and Magnum.
But Ms Gobbo, who acted for Mokbel in the Orbital case, was a secret underworld informer who gave handlers information about her clients even as she represented them in court.
Her informing as 'Lawyer X' led to a nearly two-year, multi-million dollar royal commission into Victoria Police's use of informers.
Mokbel has been fighting to overturn the Quills, Orbital and Magnum convictions since 2013, with the Court of Appeal and High Court both rejecting earlier appeal bids.
But three Victorian Court of Appeal judges have ruled that Ms Gobbo's conduct and that of investigating police should be examined by a Supreme Court judge.
Whether Victoria Police or Ms Gobbo engaged in improper conduct, or even broke the law, during Mokbel's investigation, extradition from Greece and eventual prosecution is just one of 20 matters for the trial judge to determine.
The judge has also been asked to look at whether that conduct was part of deliberate or systemic improper or illegal practices at the highest levels of the police force.
The scrutiny will even extend to state and federal directors of public prosecutions, with Mokbel's legal team asking when they realised or should have known that his extradition and prosecution had been tainted by Ms Gobbo's snitching.
"We do not accept that the applicant should be denied the opportunity of establishing that any relevant impropriety on the part of police or prosecuting authorities was intentional, or systemic," Friday's judgment stated.
Mokbel's legal team want to know how strong the case against him would actually have been were it not tainted by Ms Gobbo, and whether Mokbel would have accepted a plea deal had he known she was snitching.
The answers to these questions, likely to be heard in the Supreme Court in August, will determine whether the Court of Appeal will allow Mokbel to mount a second appeal bid on the Quills, Orbital and Magnum prosecutions.
His lawyers contend he is a victim of a miscarriage of justice because police paid crown witnesses and broke the law in recruiting Ms Gobbo, while she provided detectives with confidential information.
It's claimed the police also acted unlawfully during the course of Mokbel's infamous 2007 extradition from Greece, where he had fled days before his trial on cocaine charges was due to finish.
Mokbel has already had another conviction and 12-year jail term overturned, due to Ms Gobbo's involvement in his case.
Previous appeal hearings have been told he is enduring onerous conditions in prison since a near-fatal attack in February 2019, in which he suffered a traumatic brain injury.
Mokbel, wearing a suit jacket, sat at a desk in a room at Barwon Prison to hear Friday's decision.
