“When you’re 10 years old and that happens to you — I pretty much sublimated that from my existence,” he said. “I don’t like to think about it, because to me it was so unfair. Painful things you kind of just block from your consciousness, and that was one of them.”

Mr. Okui, 86, is a retired history teacher who taught for decades at Canoga Park and Gardena high schools. For more than 30 years he has also led annual tours to the former campsite at Manzanar and taught workshops at United Teachers Los Angeles to help guide public-school teachers on how to educate their students about Japanese internment.

Last year, Gov. Jerry Brown signed the Civil Liberties Public Education Act, which provided $3 million in state funding to expand education on Japanese internment. The legislation aims to link historic civil rights violations “with current civil liberties challenges.”

“We have to remember that the incarceration of over 120,000 Japanese Americans without any due process of law began with an executive order, much like the ones that President Trump has been issuing,” Al Muratsuchi, the State Assembly member who sponsored the bill, said in 2017.

For Mr. Okui, news of President Trump’s Muslim ban in 2017 and the separation of immigrant children from their parents in recent weeks distressed him.