In China’s cotton-growing Xinjiang region, farmers have been hailing a bumper harvest this autumn. But much of the crop is under U.S. sanctions, and where it will end up is a thorny question.

Xinjiang produces a whopping 85 percent of China’s cotton, which is made into garments sold around the world. Some of the largest Xinjiang suppliers have been banned since last year from selling to the United States because of human rights abuses in the region against members of the Muslim Uyghur ethnic minority.

U.S. and European policymakers are now discussing expanding the ban, with much of the world’s cotton products hanging in a regulatory and ethical gray zone. Enforcement is proving challenging, with fashion brands sourcing from hundreds of factories around the world with little proof of where the cotton originated.

Laura Murphy, professor of human rights and contemporary slavery at Sheffield Hallam University, says there is high likelihood that banned Xinjiang cotton is still making it to U.S. shelves, because it is shipped to third countries for clothing manufacturing.