This paper gives an overview of the history of the application of Islamic criminal law in northern Nigeria, and the programs of “Sharia implementation” begun by twelve northern states in 1999-2000. The new Islamic criminal law statutes enacted by the twelve Sharia states are then described in more detail, and constitutional and other anomalies relating to their application are discussed. Among the anomalies is the fact that although the harsh sentences are being imposed by Sharia courts, they are not being carried out, with the result that hundreds of convicts are serving indefinite terms of imprisonment to which they were not sentenced. The article concludes with a discussion on how this problem is likely to be handled in the medium term and resolved in the long term.