The term GSC means Ground Security Coordinator. They are the persons that are representing the airlines in issues of security. They are the ones that tell you that you cannot fly. When TSA finds something wrong that warrants calling the GSC to make a determination about the issue, the TSA can make a recommendation to the GSC about whether or not the passenger should fly. This is according to federal law and also according to that law, the GSC is not allowed to over ride TSA recommendations.