Site administrators and other users can use the People Picker Web control to select people and groups when assigning permissions. You can use the setproperty and getproperty operations to define the scope of the People Picker Web control to an Active Directory directory service organizational unit. When information about users is located on multiple forests, additional steps might be necessary to ensure that all people and groups are available from this Web control. You are permitted to select users only on the domain on which Windows SharePoint Services 3.0 is installed.
For more information about People Picker, see Peoplepicker Properties.