 Buchanan and Keohane agree that the attempt to rule without legitimacy is an unjustified exercise of power. They also argue that the attempt to rule without legitimacy raises not only a normative problem, but has direct practical consequences, as institutions that appear unjustified will not be effective. The problem of legitimacy that global governance institutions face is that even when there is widespread agreement that global institutions that can take on the role of co-ordination devices are necessary, there will be widespread disagreement about which particular institutions are necessary and what rules they should issue (Buchanan and Keohane 2006: 408ff).