Safeguards and Regulators

The BP oil spill incident has thrown up an interesting fact. While regulators in two major oil-producing countries, Norway and Brazil require acoustic switches to activate an underwater valve that shuts down the well even if the oil rig itself is damaged or evacuated, the US regulators do not require them. Norway has had acoustic triggers on almost every offshore rig since 1993. How do regulators decide what is necessary? I suspect this again has to do with study of safety integrity levels and the perception of risk. Read the full article in this link