By Michael Polt and Kim Davis

As the Trump administration revises America’s visa system to prevent abuse—such as instances in which companies bring foreigners into the U.S. to replace native workers at lower pay—one category stands out as deserving of protection: J-1 visas, for “exchange visitors.”

This broad designation covers trainees, interns, exchange students, visiting scholars, au pairs, camp counselors and the like. J-1 visas are always time-limited. They often carry a requirement that the visitor return to his home country for a fixed period, typically two years, before coming to the U.S. again. Over the past five years, an average of 325,000 such visas were issued annually.

People on J-1 visas are prohibited from holding permanent jobs here. Rather, the visas provide an opportunity for cross-cultural education and training. The idea is that when visitors return home, they bring with them the American values they were exposed to during their stay. Many J-1 visas go to young people who develop an appreciation for life and culture in the U.S. They become America’s de facto ambassadors and advocates abroad.

Amb. Polt, a senior director at the McCain Institute for International Leadership, was U.S. ambassador to Serbia and Montenegro (2004-07) and Estonia (2009-12). Mr. Davis is chairman of the board at the Baltic-American Freedom Foundation.