Cloud computing introduces a radical change in computer resources services that may become the best service provider at a reduced cost to the users. In spite of all the advantages of cloud computing, there are a lots of security challenges that come with its implementation. In overcoming these challenges, there are many access control models proposed in literature; these include discretionary access control, mandatory access control and role based access control. Role based access control models use role hierarchies and constraints. Administrative roles can be designated to manage other roles.