Nigeria’s Supreme Court on Friday overturned a lower court ruling dismissing terrorism charges against a popular separatist leader whose trial has been blamed for an outbreak of violence in the country’s southeast region.

The Court said Nnamdi Kanu, leader of the Indigenous People of Biafra (IPOB) separatist group that seeks independence for Nigeria’s southeastern region, still faces terrorism charges despite the lower court ruling. Kanu, who also holds British citizenship, has already pleaded not guilty to the charges.

In announcing the decision, Justice Garba Mohammed said that although Nigeria’s secret police violated Kanu’s rights during his arrest and extradition from Kenya in 2021, the Court of Appeal was wrong to rule in October last year that the violation was grounds for the dismissal of the charges.

“No legislation in the country stripped the trial court of the jurisdiction to go ahead with Kanu’s case, despite the illegal action,” of the secret police, the justice said. The trial of the separatist leader, who also holds British citizenship, is expected to resume next year.

Kanu has remained in detention since the Court of Appeal’s ruling.

The Supreme Court decisoin further complicates the fate of Kanu who has been in and out of jail since 2015 when he was first arrested and charged with terrorism and treason. He has denied any wrongdoing and his supporters have accused the government of unjustly targeting him to clamp down on the group’s separatist campaign.

The IPOB campaign for an independent state of Biafra follows the short-lived Republic of Biafra which fought and lost a civil war from 1967 to 1970 to gain independence from Nigeria. An estimated 1 million people died in the war, many from the southeastern region.

However, the Nigerian government has said the country’s unity is “not negotiable” and has often accused Kanu’s group of instigating violence in the southeast, often by imposing lockdowns and targeting prominent people in the region. Dozens have been killed this year in the violence blamed on IPOB, which the group denies.