Mohammed Liman, the judge, granted an application moved by Mr Kalu’s counsel Lateef Fagbemi, seeking his release.
The Economic and Financial Crimes Commission (EFCC) did not oppose the application.
In an amended 39 counts charge, they were accused by the Economic and Financial Crimes Commission of conspiring and diverting over N7 billion from the coffers of the state.
Following the nullification of his conviction by the Supreme Court on May 8, the former governor filed an application at the federal court seeking his an order for his release from the custody of the Nigerian Correctional Service (NCS), Kuje, Abuja.
Mr Kalu had been accused of stealing and mismanaging funds belonging to Abia State during his days as governor between 1999 and 2007.
He pleaded not guilty but was sentenced in December 2019 to 12 years in prison.
He was jailed alongside Ude Udeogu, who was the director of finance and accounts at the Abia State Government House during Mr Kalu’s tenure.
The duo appealed the convictions by the Lagos Division of the Federal High Court up to the Supreme Court.
On May 8, the Supreme Court ordered a retrial of the case.
A seven-member panel of the apex court, in a unanimous verdict delivered by Justice Ejembi Eko, invalidated the conviction.
Justice Eko declared that Justice Mohammed Idris, who convicted the duo was already a justice of the Court of Appeal when he ruled and sentenced Mr Kalu and his co-defendant.
He held that a Justice of the Court of Appeal cannot operate as a judge of the Federal High Court, and ordered the Chief Judge of the Federal High Court to reassign the case for trial, the report said.
The apex court said section 396 (7) of the Administration of Criminal Justice Act (ACJA), 2015, on which the former president of the court of appeal, Zainab Bulkachuwa, relied on to authorise the trial judge to return to the high court to conclude the trial was unconstitutional.