How to restrict users from creating assets in a certain category?

User wants to create a new Role with 'Create assets', 'Forums administration', or 'Publishing administration' permissions and with a specific category. But, iRAM throwing an error like following

"A combination of a classification constraint with any of the entitlements Create assets, Forums administration, or Publishing administration is not valid. The test would never be true since no existing asset is involved when using these entitlements."

Is there any way to limit external users the ability to create assets in a specific category?