"They worked in sweltering heat for Exxon, Shell and Walmart. They didn't get a dime." 

A nationally renowned drug rehab program in Texas and Louisiana has sent patients struggling with addiction to work for free for some of the biggest companies in America, likely in violation of federal labor law. The Cenikor Foundation has dispatched tens of thousands of patients to work without pay at more than 300 for-profit companies over the years... [P]atients have moved boxes in a sweltering warehouse for Walmart, built an oil platform for Shell and worked at an Exxon refinery along the Mississippi River. “It’s like the closest thing to slavery,” said Logan Tullier, a former Cenikor participant who worked 10 hours per day at oil refineries, laying steel rebar in 115-degree heat. 

... All participants have to do is surrender their pay to cover the costs of the two-year program. But the constant work leaves little time for counseling or treatment, transforming the rehab into little more than a cheap and expendable labor pool for private companies... At some job sites, participants lacked proper supervision, safety equipment and training, leading to routine injuries... [I]n a statement, Cenikor officials said the work provides “a career path for clients to be hired by companies who traditionally do not hire those with felony convictions, allowing them to return to a life of being a responsible, contributing member of society.” They said they follow all state and federal laws... Many Cenikor participants work for a network of subcontractors that then dispatch them to the major companies... Walmart said it found Cenikor’s labor arrangement troubling and pledged to investigate... Exxon said...  the company “contractually requires all of our suppliers to comply with all applicable environmental, health, safety and labor laws for themselves and their subcontractors.”