Advocacy groups have weighed in on a lawsuit against the nation’s second-largest for-profit prison provider, arguing in recently filed “friend-of-the-court briefs” that GEO Group Inc.’s alleged practices of relying on cheap and unpaid labor by detained immigrants underscores abuses to this vulnerable community.

Attorneys who filed the lawsuit in 2014 are currently fighting to uphold class certification in the case before the U.S. Court of Appeals for the Tenth Circuit. The U.S. District Court for the District of Colorado in Denver originally certified the class, which could include as many as 60,000 detainees who cycled in and out of the GEO Group-owned Aurora Processing Detention Center in since 2004.