I know it's difficult to maintain methodological consistency over many years of cases, but one might expect to see some basic level of consistency over, say, a month. But even that can be tough.
In today's opinions, Justice Thomas joins a concurrence by Justice Scalia, which chides the Court for relying on the Advisory Committee Notes to a Federal Rule of Criminal Procedure. The Notes are not authoritative, Justice Scalia complains -- only the text of the rule matters. But it wasn't even a month ago that Justice Thomas joined, without comment, a Court opinion that relied on Advisory Committee Notes to a Federal Rule of Civil Procedure, even though Justice Scalia concurred separately, raising the same point. (As I said at the time, Justice Scalia is extending his anti-legislative history campaign somewhat unthinkingly here, but that's another story.)
Are the Criminal Rules so different from the Civil Rules? I don't think so. It looks more like Justices don't sweat every detail of the opinions they join. In today's case, Justice Thomas may have joined Justice Scalia's opinion primarily for its bigger difference with the Court's decision (Justice Scalia thought part of the statute at issue was unconstitutional), and he may not have cared so much about this interpretive methodological detail. The big issue wasn't present earlier this month when Justice Thomas went along with consulting Advisory Committee Notes -- again, perhaps without really intending to commit himself on that particular point.
I know a foolish consistency is the hobgoblin of little minds, but these methodological issues do matter, and a little consistency on them would be welcome.