Project Server 2010 includes the new Project Permission feature so that by-default, Project Managers can directly control who has access to the projects that they own. For more information about the Project Permissions feature, see the Project Server 2010 – Project Permissions blog posting.
The ability to directly add or remove permissions to a project is controlled by the Manage Basic Project Security category permission. Given that this is a category permission, it means that it is possible to grant this permission for one project yet deny it for another project or more commonly, to grant it for a group of projects yet deny it for a different group of projects.
By default, the following groups have the Manage Basic Project Security permission enabled on the noted category:
How do you enable or disable this permission? The following steps show you how you could, for example, deny Portfolio Managers from creating project permissions. A similar approach is taken to enable or remove the permission for a group or user.
As noted, you can use a similar process to add the Manage Basic Project Security permission to other users or groups. But do note that that though you can control this permission directly on a category on a user account, for easier manageability it is recommended that you control this at the security group level.
I need to Know, How to go back the original conditions about the global permissions?