Cannot disassociate subnets from NAT gateway

You’re hitting an Azure RBAC + deny assignment conflict when trying to remove the NAT Gateway. Let’s break down what the error is really saying and how you can resolve it:

🔎 What the error means

• You have permission:

Your account (live.com#{email}) can perform Microsoft.Network/virtualNetworks/write on the VNet (workers-vnet).

• You do not have permission:

You’re missing Microsoft.Network/networkSecurityGroups/join/action on the NSG (workers-sg). This action is required when Azure tries to detach or reconfigure resources linked to the NSG during NAT Gateway removal.

• Blocked by deny assignment:

Even if you had RBAC permissions, there’s a deny assignment on the NSG scope. Deny assignments override RBAC and prevent certain actions — often created by Azure-managed services (like Databricks or policy enforcement).

⚙️ Why this happens

• Databricks-managed resource groups (databricks-rg-*) often have locked-down NSGs with deny assignments to prevent accidental modification.
• When you try to remove the NAT Gateway, Azure attempts to update the NSG association, but the deny assignment blocks it.you’re hitting an Azure RBAC + deny assignment conflict when trying to remove the NAT Gateway. Let’s break down what the error is really saying and how you can resolve it:

🔎 What the error means

 - You have permission:  
 

Your account (live.com#{email}) can perform Microsoft.Network/virtualNetworks/write on the VNet (workers-vnet).

 - You do not have permission:  
 

You’re missing Microsoft.Network/networkSecurityGroups/join/action on the NSG (workers-sg). This action is required when Azure tries to detach or reconfigure resources linked to the NSG during NAT Gateway removal.

 - Blocked by deny assignment:  
 

Even if you had RBAC permissions, there’s a deny assignment on the NSG scope. Deny assignments override RBAC and prevent certain actions — often created by Azure-managed services (like Databricks or policy enforcement).

⚙️ Why this happens

• Databricks-managed resource groups (databricks-rg-*) often have locked-down NSGs with deny assignments to prevent accidental modification.
• When you try to remove the NAT Gateway, Azure attempts to update the NSG association, but the deny assignment blocks it.

Hi @ Pawel Lewandowski •,

Welcome to Microsoft Q&A Platform

This behavior is expected and by design when working with Azure Databricks–managed resources.

When an Azure Databricks workspace is created, Azure automatically provisions a Databricks-managed resource group (MRG). This managed resource group and its associated resources (VNets, subnets, NSGs, disks, NAT Gateway, etc.) are protected by system-generated deny assignments.

That is why the operation fails with:

Microsoft.Network/networkSecurityGroups/join/action

• Even though you have sufficient RBAC permissions, the deny assignment blocks changes such as disassociating a NAT Gateway from a subnet.
• The deny assignment is not created by an Azure Deployment Stack
• It cannot be removed or modified manually
• Assigning higher roles (Contributor/Owner) will not resolve the issue
• Direct deletion of the Databricks-managed resource group is not supported

To resolve the issue :

• Delete the Azure Databricks workspace that created the managed resource group
  • This is the only supported way to remove the deny assignment and the managed RG.
• If you require full control over networking resources: Recreate the Databricks workspace using a custom VNet configuration.

Refer the links which are related to same issue:

Fixing issue of Deny assignment with azure databricks
Deny assignment modification to allow attach/detach of disks in azure databricks
Deny Assignments in Azure

I hope this information helps resolve your issue. Please feel free to ask if the provided solution does not help or if you have any additional questions.

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