Much has now been made of a fairly spectacular blunder made by Justice Scalia in his dissent in the EME Homer case announced last week. Scalia opined that EPA was trying to smuggle cost considerations into rulemakings under the Clean Air Act. He also said it was not the first time that EPA had tried this little bit of chicanery, and he cited Whitman v. American Trucking as an example. The problem is that EPA's position was the exact opposite, as Scalia's own opinion reflects. Scalia also ignores another of his opinions in Entergy v. Riverkeeper, in which EPA declined to mandate a very expensive technology on cost considerations. Granted, Scalia is the author of a large number of opinions (over 1000), so maybe he should get a break. Still, Dan Farber notes the casual nature of the writing from his dissent ("Look Ma, no hands!" "Wow, that's a hard one -- almost the equivalent of asking who is buried in Grant's Tomb") that is really unusual for a Supreme Court opinion. Perhaps Justice Scalia is, in his advancing years, shedding the few inhibitions he still has.
There are other aspects of Scalia's opinion which suggest a more significant about-face. The broader about-face is what seems to be an about-face in "conservative" (they would call themselves that, I am not sure I would) circles on cost-benefit analysis, as cost-benefit analyses start to make some regulations look sensible, like climate policy. The dismay over the social cost of carbon is a driver of that movement. But we should not be surprised that "conservatives" have discovered postmodernism late in their intellectual lives, including that of climate skepticism. As Eric Rasumussen points out, arguing over facts is more personal than arguing over theories. My view is that "conservatives" sense they are going to be on the losing end of empirical arguments, and are driven less by data than by ideology.