Government watchdog group Public Citizen has asked Congress to investigate whether investor Carl Icahn should have been subject to lobbying disclosure laws when he advised the president on the U.S. biofuels program. Icahn is an unpaid adviser to President Donald Trump and submitted a proposal to change the point of blending under the Renewable Fuel Standard away from refiners and further down the supply chain. Because Icahn owns a controlling stake in a refinery that stands to benefit from the proposal, he may be required to disclose his discussion on the subject as lobbying under a 1995 lobbying disclosure law, according to Reuters. The group made the investigation request in a letter sent to Congress Wednesday morning. The White House has said it is reviewing Icahn’s proposal and has not yet taken a position.