By default, Structure is accessible to anyone who has Browse permission on structure-enabled projects. You can further restrict this access level to one or more user groups.
To select who can use Structure:
Which projects are enabled for the Structure also affects Who Has Access to the Structure.
When Structure is enabled for anyone, even anonymous visitors will have access to Structure. It means that even if they don't have access to projects and will not see any issues in the structure, they will still see the Structure name and may see the Automation settings. To make Structure accessible to only logged in users, restrict access to jira-users group.