You can specify who tasks can be assigned to by container. When users create a task in that container, only the users you specify are available in the Assign To list.

You can specify task assignees while you are creating a container, or you can set them later by right-clicking on the Project in the navigation tree and going to Configure > This Container.

1. Expand Task Assignee.
2. Click the Quick Search or the Advanced Search to find and select users.
3. Click Finish.

Only the users you added appear in the Assign To list when creating tasks in this container.