3.1.4.4 Removing Folder Permissions
To remove an entry from the folder's permissions list, the client MUST retrieve the existing permissions list as specified in section 3.1.4.1 to get the values of the PidTagMemberId properties that are assigned to the users in the permissions list.
The client MUST send a RopModifyPermissions ROP request ([MS-OXCROPS] section 2.2.10.1) with the RemoveRow flag set in each PermissionData structure that specifies a user to be deleted. The PropertyValues field of the PermissionData structure MUST include only the PidTagMemberId property (section 2.2.5).