Hello Sam Titmuss,
Thank you for reaching out to Microsoft Support!
According to the documentation, the Graph API does not provide an endpoint for deleting a resource assignment in the Catalog.
You can delete a Catalog through the Catalog endpoint, but it is not possible to do more elaborate operations, as shown below:
Reference document:
https://learn.microsoft.com/en-us/graph/api/resources/accesspackagecatalog?view=graph-rest-1.0
Hope this helps.
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