Kanu, a British citizen who leads the banned Indigenous People of Biafra (IPOB), disappeared from Nigeria after skipping bail in 2017. He was arrested in Kenya in 2021 and charged with terrorism.
Friday's ruling by Judge Lawal Garba reinstating Kanu's seven-count terrorism trial at a lower federal court has effectively extended his detention, which began two years ago after his arrest.
"Even though illegalities were committed with the deployment of brutal force to invade his home after he was granted bail and the extraordinary rendition (from Kenya) into the country, there is no legislation yet that has ousted the jurisdiction of the court to try him," Garba said.
Kanu had denied the charges of terrorism and knowingly broadcasting falsehoods, which are linked to social media posts he issued between 2018 and last year.
Kanu's IPOB campaigns for the secession of a part of southeastern Nigeria where the majority belong to the Igbo ethnic group. Nigerian authorities have labeled IPOB a terrorist organisation.
An attempt by the southeastern region to secede as the Republic of Biafra in 1967 - the year that Kanu was born - triggered a three-year civil war that killed more than 1 million people.
By Camillus Eboh, Reuters
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