The ruling by the Federal High Court comes barely two months to the general elections slated for February 2015.
The suit was instituted by Victor Emenuwe, Onome Inaye, Kabiru Abu, Osagie Iyekepolor, Modugu Odion (for and on behalf of inmates of Nigerian prisons), against the Independent National Electoral Commission (INEC) and the Comptroller-General of Nigeria Prisons Service.
The plaintiffs had asked the court to determine whether having regards to the provisions of section 25 of the Constitution of the Federal Republic of Nigeria 1999, the plaintiffs are not entitled to be registered as voters by the 1st Defendants.
In his judgement, Justice Mohammed Lima said, “To deny inmates the right to vote is unconstitutional, illegal, irregular, unlawful, null and void and of no effect whatsoever.
“Being an inmate is not an offence that impedes their registration and voting right under section 24 of the Electoral Act,” he added.
The Judge ordered the Independent National Electoral Commission to update its register of voters to take into account the prison population.
The court also directed the defendants to ensure that the applicants are not disenfranchised.
The February 14 presidential election would pitch incumbent President, Goodluck Jonathan, against his strongest challenger and former military Head of State, General Muhammadu Buhari.
President Jonathan had recorded a victory over General Buhari in 2011, amid claims of rigging.