In a unanimous ruling, the Court of Appeal in Abuja declared the governorship election in Zamfara State that produced Governor Dauda Lawal as inconclusive.
The court also ordered a re-run in three local government areas of the state, including Maradun, Birnin-Magaji and Bukyun.
The ruling followed an appeal brought before the court by the All Progressives Congress (APC) candidate and immediate past state governor, Bello Matawalle.
INEC had declared Lawal the contest winner, defeating the incumbent in a shocking outcome.
The APC had challenged the victory at the Zamfara State Governorship Election Petitions Tribunal but lost.
However, the Court of Appeal overturned the tribunal’s decision and ordered a re-run in the affected areas.
The court held that the tribunal did not consider the APC’s evidence in affirming Lawal’s victory.
The court also faulted INEC for relying on information it obtained from its INEC Result Viewing (IReV) portal to collate the final result of the governorship election.
A fresh election will also be conducted in polling units whose results were not counted in the final tally.
The judgement is a setback for Lawal and the Peoples Democratic Party (PDP), who had hoped to consolidate their hold on power in the state.
It is also a blow to INEC, which has been accused of incompetence in the conduct of the election.
The re-run is expected to take place in the coming weeks.
It is unclear whether Matawalle will resign as Minister of State for Defence to contest the re-run.