Under section 22 of the Land Use Act 1978, all land in a state is vested in the Governor, and no holder may transfer it without the Governor’s consent.
Practically: a sale, mortgage or assignment without consent is not a completed transfer, whatever the parties signed. Lagos charges a consent fee of 1.5% of the property’s value.
Nobody in Nigeria owns land outright. What a C of O grants is a leasehold, conventionally of 99 years.