Hi @Glenn Maxwell
Thanks for posting your query!
If you delete a sensitivity label from the Microsoft Purview portal or the Microsoft Purview compliance portal, the label isn't automatically removed from content, and any protection settings continue to be enforced on content that had that label applied.
If you edit a sensitivity label, the version of the label that was applied to content is what's enforced on that content.
For detailed information about what happens when you delete a sensitivity label and how this is different from removing it from a sensitivity label policy, see Removing and deleting labels.
If the label applied encryption, the underlying protection template is archived so that previously protected content can still be opened. Because of this archived protection template, you can't create a new label with the same name. Although it's possible to delete a protection template by using PowerShell, don't do this unless you're sure you don't need to open content that was encrypted with the archived template.
Remove-AipServiceTemplate
-TemplateId <Guid>
[<CommonParameters>]
Ref Doc:
https://learn.microsoft.com/en-us/purview/sensitivity-labels
https://learn.microsoft.com/en-us/powershell/module/aipservice/remove-aipservicetemplate?view=azureipps
I hope this information helps. Please do let us know if you have any further queries.
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Thank you.