ATLANTA (AP) — Workers at auto plants in the South should be free to unionize without pressure from employers or anti-union governors, acting U.S. Labor Secretary Julie Su said Thursday, even as some southern states pass laws to inhibit organized labor.

“That choice belongs to the worker, free from intervention, either by the employer or by politicians, free from retaliation and threats,” Su told The Associated Press in an interview Thursday in Atlanta. “And what we are seeing is that workers who were thought to be too vulnerable to assert that right are doing it, and they’re doing it here in the South.”

The United Auto Workers union vowed a broad campaign to organize southern auto assembly plants after winning lucrative new contracts in a confrontation with Detroit’s automakers. Last week, 73% of those voting at a Volkswagen AG plant in Chattanooga, Tennessee chose to join the UAW. It was the union’s first in a Southern assembly plant owned by a foreign automaker.