During a Q&A Session at a Case Western Reserve University event, Judge John E Jones III gave an anecdote about Justice David H Souter giving a tour of the Supreme Court to a Russian Judge. In this particular story he was recollecting, Justice Souter said he believed the most important Supreme Court case was Brown vs. Board of Education. The Russian Judge disagreed and said it was United States vs. Nixon.
I can't find, with internet searches, that this exchange really happened. I am not, at all, questioning Judge John E Jones III, as he is simply re-telling a story that was told to him.
Are there any reliable sources that can corroborate this account?