Hi @Linares Carramolino, Maria Concepción
Thank you for posting this in Microsoft Q&A.
I understand you want to assign a policy to the tenant root management group from a new user account.
At least one of the roles - Owner, Resource Policy Contributor, or User Access Administrator must be assigned to the user account in order to assign policies to the tenant root management group.
For your reference: https://learn.microsoft.com/en-us/azure/governance/management-groups/overview#management-group-access
To Assign a policy to the tenant root management group follow the steps which mentioned in this document: https://learn.microsoft.com/en-us/azure/governance/policy/tutorials/create-and-manage#assign-a-policy
Hope this helps. Do let us know if you any further queries.
Thanks,
Navya.
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