Players who sign up after the week 1 deadline or any subsequent week will have to be approved by the manager, regardless of the 'Manager Approve' setting. Managers should always receive an email when anyone tries to join their league. They will also see a notification of new signups on the League home page and in the Manager Control Panel.
The only exception are weekly pickem or weekly confidence pools (see Running a Weekly Pickem Pool). In this case, players can sign up without approval throughout the season provided the manager has 'Manager Approve' set to 'No'.