The code you included will return a SOAP fault to the client with the specified fault code and message. Since this is a Business Service, it will also log the fault to the Ensemble Event Log, along with the last error the process encountered (%objlasterror). This appears to be where this is where the error message is coming from.
Note that, again, since this is a Business Service, you can use the ReturnStatusFault() or ReturnMethodStatusFault() methods to create and return the SOAP fault instead of creating it manually. This should have the same behavior as your code, except that the fault code and message may be different. See the documentation here:
I'm not really sure that I answered your question. Can you give more information about the problem you are trying to solve?