(CNN)--Jeff Wasserstrom is a self-proclaimed China specialist who is seriously considering never returning to China -- at least, he says, not while President Xi Jinping is in power.

The American professor, who for decades made multiple trips a year to China and was last there in 2018, hasn't focused his career on Tibet or Taiwan -- lightning-rod issues which attract Beijing's ire at lightning-quick speed -- but he has written about cultural diversity and student protests in mainland China, and appeared on panels with people he says the Communist Party is "clearly upset with."

Three years ago, that made the California-based academic wonder if his visa application to China might be rejected.

Today, it makes him consider whether crossing the border risks his indefinite arbitrary detention. The chance of that outcome, Wasserstrom says, might be "pretty minimal," but the consequences are so grave -- those detained can be locked up for years without contact with their families or a trial date -- he is not willing to gamble.

And he is not alone.