A federal judge in Colorado has approved the first class-action lawsuit testing whether private prisons can force detained immigrants to work as “volunteers” for as little as $1 per day. The case centers on an ICE detention facility run by the GEO Group, one of the country’s largest private prison operators, and may turn on whether detainees are considered the same as inmates convicted of crimes.

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Correction (March 7, 2017): A previous version of this story misstated the amount that detainees make. The text has been corrected.