Slab provides a flexible topic permission system to let you control read and edit permissions to the topic and the posts inside. It also covers a wide range of access-level, allowing you to hide a topic from everyone, or to share it with everyone on the Internet.
Topic Access
Topics can have one of the following access levels:
Open - Anyone can see posts within the topic. Open topics can have any type of subtopics.
Private - Only members can see posts within the topic. Private topics can only have private or secret subtopics.
Secret - Only members can see that the topic exists. Secret topics can only have secret subtopics.
Public - Anyone with the URL can see posts within the topic, without needing to log into Slab. Public topics can only have public subtopics.

Membership
Topic members can:
Receive notifications for post edits and newly published posts
View its posts
They could also perform edit actions if the permission setting allows (more on this below):
Edit its posts
Add and remove other members
Edit the topic including name, description, banner image, privacy, pinned posts, and subtopic order

Some topic members can also be owners who in addition can:
Add and remove owners
Set whether or not regular members can edit the topic
Slab admins can join any open, private, or public topic (by override or request to the owners) and make themselves or others an owner. However, admins must be explicitly invited to join secret topics.
Edit vs Read
You can restrict who can edit a topic and its posts through topic membership and ownership. Configure this in the topic's Edit Topic modal.
This is individually configurable in each topic and is not inherited by subtopics. An editable parent topic may have uneditable child topics and an uneditable parent topic may have editable child topics.

Topic edit enables:
Modifying the name, description, banner image, and "Organize under"
Modifying the "Who can access" or "Who can edit" settings
Reorganizing the subtopics
Deleting the topic
Pinning posts or reordering pinned posts
Topic edit does not restrict:
Adding or removing members — any member can add/remove other members, any owner can add/remove other owners
Inheriting members from the parent topic — this is considered a special case of adding or removing members
Adding or removing a post from the topic — the posts themselves specify which topic they are organized in
Adding or removing subtopics — the subtopics themselves specify which topic is its parent, not the other way around. Note this means an editable subtopic can be added to an uneditable topic
Post edit enables:
Modifying the post title and contents
Deleting the post
Adding or removing topics (must also be able to edit the topic)
Post edit does not restrict:
Commenting on the post