Using Federated AD RMS with SharePoint Server 2007

Microsoft Office SharePoint Server 2007 together with federated Active Directory Rights Management Services (AD RMS) provides a secure, efficient and easy-to-use means to collaborate within an organization and with external partners. Office SharePoint Server supports the automatic application of information protection policies to documents that are downloaded from a SharePoint document library. When combined with Active Directory Federation Services (AD FS), this allows a company to publish documents in a SharePoint library and keep control of who can access those documents and how they can use them, and this control extends even to users from other companies without the requirement to provision accounts for those users.

https://technet.microsoft.com/en-us/library/ee256065(WS.10).aspx