He's not going to be criminally prosecuted for libel. He's going to be civilly sued for libel.
Edit: So, funny story negating my previous sentence. While US citizens are protected from libel prosecutions from other countries, there are a few states that still allow prosecution if the victim resides in that state. If I were going to libel anyone, I would avoid doing it to anyone- especially a female lawyer (see below)- in those states. Guess what one of those states is? In fact, guess which state is the one that has brought the most libel cases? Yep, Virginia, where Sandford is based. The statute there is archaic and reads, in part:
Since it's a class 3 misdemeanor it doesn't carry a harsh punishment; $500 maximum, no jail. Much more worthwhile to launch a civil action.
But either way there's a good chance he'll be criminally prosecuted for various other offenses like failing to obey a peace order, contempt of court, etc. when he continues to think he is above the system.
He might also catch a harassment charge if he's actually been contacting these people at their workplaces.