HE (and the rest of the passengers) are lucky the pilot didn't land at the closest airport (RE ANCHORAGE) and off load him there to the FBI....Ive now had that happen TWICE this year (but never before) on NRT-JFK flights (Both ANA though) and its not a pleasant experience.
Both times we sat for 5-6 hours after landing due to NH having to file new flight paths, as well as waiting for alternate landing sites in Canada to open in the morning (I didn't get this part as flights fly overnight between US-ANC all the time)
But when questioned I was told by both the pilots and the Ground Service Agent NH pulled out of bed that Canada is like the middle of the ocean at night and there still must be alternate landing sites avail between ANC-NYC