Resource & in plant & is already being used

What causes this issue?

You are attempting to set the maintenance rule for a standard value to
"cannot be entered". This is not possible because this resource is used
in recipes where standard values are maintained.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Error message extract from SAP system. Copyright SAP SE.