Enforcement of Separation Of Duty (SOD) rules for the enterprise is very complicated when it is done per application. For each application like SAP, Oracle eBS, Peoplesoft or JD Edwards the SOD rules would have to be defined. But there is no sight on the overall SOD rules that would prevent a person to have rights in the Peoplesoft HR as well as the SAP order management or General ledger.
Theoretically it would be possible to have a meta SOD system to enforce these kind of rules. But that would be complex to implement and use. When a user would get a role it would need to be checked in the specific systems as well as the meta system.
The solution is in the future of Service Orientation. When would would have an authorization service for the total enterprise the SOD rules could be enforced in this service. Each application like SAP, EBS or Peoplesoft would check the authorization level of the person in the authorization service.
That would mean a change in architecture for the different ERP application. Oracle is working on that in their fusion applications. The authorization server used by the authorization service they already have. They got it through the Bea systems acquisition. It is the former aqua logic server now called Entitlement server.