WillowRun, the investigation board typically has no rule making authority - however it can issue 'recommendations'. The regulatory authority then reviews those recommendations and determines what (if any) action to be taken based on those recommendations.
So, in the US, the NTSB makes recommendations and the FAA determines what action to take as a result. This has sometimes resulted in considerable friction between the NTSB and FAA when the FAA determined the NTSB recommended action was not justified.