The last time we heard from Rabbi Leib Tropper, the ultra-Orthodox rabbi and conversion specialist, he was caught up in both a sex scandal and a multi-million-dollar court battle between the billionaire Thomas Kaplan, chair of the 92nd Street Y board, and his nephew, Guma Aguiar, the former owner of the controversial Beitar Jerusalem soccer team who disappeared off his yacht last year in Florida. Tropper, accused of trading Jewish conversion papers for sexual favors, was forced to leave the Rockland County enclave of Monsey in disgrace.

But that was 2010. Now, Tropper is back, apparently lecturing and teaching at a Staten Island yeshiva headed by Reuven Feinstein, who declined to condemn Tropper at the height of the controversy and who, perhaps not coincidentally, was...