At the Shu Le County Education Center, a sprawling three-story complex in China's far-west region of Xinjiang, the dormitories feature bars on windows and doors that only lock from the outside.

Inside are hundreds of minority Muslim Uighurs who have no way of leaving without an official escort, even though Chinese officials who took a group of foreign journalists around the "transformation through education" camp this past week insisted they were there voluntarily. Asked what would happen if a Uighur refused to attend, Shu Le's principal, Mamat Ali, became quiet.

"If they don't want to come, they will have to go through judicial procedures," Ali said after a pause, adding that many stay for at least seven months.