Until the deleted users are completely erased from the database, they can be restored. Users with the 'Restore deleted users' permission can select the option by clicking on Management Console and then 'User Management' menu.

Clicking on this option will bring up a page with an interface for searching for deleted users by date deleted, keyword and associated domain:

The search results will be displayed in a table, with a 'Restore' button at the bottom. Unchecking the checkboxes for individual users will stop them from being restored.
If the user restoration is successful, the user search page will appear. If unsuccessful, a prompt will appear with the message 'User operation not performed'.

Restoring a deleted user will return all of that user's associated data to their state prior to deletion in the system. Their account will still remain archived, you will need to reactivate their account to enable them to access training again.