At an event last Wednesday, Justice Kennedy returned fire (sort of)against critics of his discussion of foreign law in his majority opinion in Roper v. Simmons, the 2004 case announcing that a "national consensus" had developed against executing juvenile offenders and that such executions had therefore become cruel and unusual punishment. At the event, Kennedy said of the fights over Roper "[t]here was kind of a 'know-nothing' aspect to the debate, it seems to me."
I won't revisit the whole dispute about the Roper majority's use of foreign law in the case, but I think it's worth remembering that one key reason (though hardly the only one) why that aspect of the majority opinion prompted so much flack is because the majority's arguments that American national public opinion had evolved to a point where a national consensus existed against the execution of juvenile offenders were almost comically weak. Put another way, the mere fact that the justices in majority turned to an examination of foreign law at all seemed to imply that even they realized there was no real evidence to support their view that a new domestic consensus had developed.
Continuing on the evolving national consensus front, the Court is faced with a case this term, Kennedy v. Louisiana (the name of the petitioner is a coincidence) , where evolving moral standards appear to support broader application of the death penalty. A lot more on that case later, but I'll point out that it will be very interesting to see whether and how Kennedy addresses that situation.