Through a lot of research I found the name of a William Araiza (on a TX Columbia Alumni list) who in one writing mentioned he attended a poli-sci seminar with Obama and in another writing claimed it was a class. Haven’t figured out which William Araiza it is from Googling though.
Most likely he's the Professor at Brooklyn College Law School or Loyola Law School in Los Angeles (same guy I assume, though at different times).
I hope you're not hanging too much on this "class vs. seminar" thing.
While there may be a technical difference, anybody who's not a snob says "class" rather than "seminar."