Cloud-20Engineering/Policies/must-have-tag.json

{
    "properties": {
        "displayName": "Must have tag",
        "policyType": "Custom",
        "mode": "All",
        "metadata": {
            "category": "Effectory Custom Policies"
        },
        "parameters": {
            "tagName": {
                "type": "String",
                "metadata": {
                    "displayName": "tagName",
                    "description": "Tag name"
                }
            },
            "allowedTags": {
                "type": "Array",
                "metadata": {
                    "displayName": "Allowed tags",
                    "description": "The list of allowed tags for resources."
                }
            }
        },
        "policyRule": {
            "if": {
                "not": {
                    "field": "[concat('tags[', parameters('tagName'), ']')]",
                    "in": "[parameters('allowedTags')]"
                }
            },
            "then": {
                "effect": "audit"
            }
        }
    }
}