Obasanjo succeeded in establishing civilian rule based on a multiparty democracy and launched a campaign against corruption, but despite a surge in oil revenues that buoyed the federal coffers, his administration faced a number of serious challenges. In 2000 religious tensions spiked following the imposition of sharia, or Islamic law, in 12 northern, predominantly Muslim states. These tensions hindered cooperation between the president and the National Assembly, among the states, and between the states and the federal government. In 2004 religious strife forced the government to declare a state of emergency in centrally located Plateau State. Ethnic strife further complicated matters, notably in the southeastern state of Benue, where tribal warfare broke out in 2001, and in the oil-rich Niger Delta, where the Ijaw tribe continues to conduct an insurgency against international energy facilities and workers. Nigeria’s image of playing a constructive role in regional stability was tarnished in 2002 when the International Criminal Court granted Cameroon control over the disputed Bakasi Peninsula, but Nigeria refused to comply with the ruling.