@Martin Hoch Thanks for reaching out to Microsoft Q&A, apologize for any inconvenience caused on this.
If a particular user is assigned with either owner or contributor access at subscription level, then he/she will be able to register all the resource provider.
If you want to limit the particular user access to register only some specific resource provider, then you can create custom role and assign the permissions as shown below.
Microsoft.web/register/action --> Register Microsoft.Web resource provider for the subscription. Microsoft.CognitiveSearch/register/action --> Register the subscription for Microsoft.CognitiveSearch provider.
For more information, refer to these documentation
- Supported different resource provider operations.
- How to create a custom roles using either Portal, PowerShell or through any other methods.
Feel free to reach back to me if you have any further questions on this.