The article goes to lengths to describe how the government, specifically the DEA are limiting supply by issuing edicts to pharmaceutical companies. Corporations don't generally defy government edicts, especially ones that lead to raids and jail time, so we really can say it's the government's doing here, rather than particularly self-limiting behavior on the part of the pharmaceutical companies.

That the government is threatening defiance of edicts with fines and jail time and not using direct means to stop additional production is not a distinction worth making - the government is limiting the supply of these medications.