I recently completed a tour of Norwegian universities, where I spoke about international law as applied to the Israeli-Palestinian conflict. But the tour nearly never happened.

Its sponsor, a Norwegian pro-Israel group, offered to have me lecture without any charge to the three major universities. Norwegian universities generally jump at any opportunity to invite lecturers from elsewhere. When my Harvard colleague Stephen Walt, co-author of "The Israel Lobby," came to Norway, he was immediately invited to present a lecture...