Collection Access Control
You can use ACLs to give Users or User Groups (and their members) permission to access a Collection via the access control panel.
An ACL can be added to a collection that will propagate to all content automatically. Thus it will be inherited if an Asset or sub-collection is in the collection that has this ACL, and any future Assets or Sub-Collections placed in the collection.
When adding the ACL to a collection, choose Propagate to all content automatically. In total you can have up to 1000 propagating ACLs.