The International Commodity Co-op was an underground trading consortium run by believers in hiding during the last 3 1/2 years of the Tribulation to help believers survive. It was formed by Chloe Williams and later headed by Lionel Whalum when Chloe was captured and executed. The Global Community considered their activities to be illegal during the cashless "mark of loyalty" period.
The Co-Op operates on a mixture of reputation credit and barter system; for example, in The Remnant, Buck asks Rayford to arrange transportation between a group of believers in Argentina wanting to trade wheat in return for purified water collected by a group of believers at the Rihand Dam, in India.
The Co-Op is shown stealing fuel for their aircraft from the Global Community in multiple occasion, usually thanks to forged work orders courtesy of Chang Wong. This would allow them to reduce their overhead and operating expenses, and justify their illegal status in the eye of the Global Community.