When the marginal social benefit curve is steeper than the marginal private cost curve, restrictions dominate. When the marginal social benefit curve is flatter than the marginal private cost curve, taxation dominates. So the sort of data French companies are reporting could be used to develop analyses to determine what sort of laws or regulations to devise. The court’s ruling against TotalEnergies, under a French law passed in 2017, expands a growing front in the global legal fight against climate change. The French ruling also marks a rare decision against a corporation in a lawsuit over climate damage.