WASHINGTON, D.C. --- Two organizations representing the ethanol industry -- Growth Energy and the Renewable Fuels Association -- are challenging California's low-carbon fuel standard in court. 

According to the Wall Street Journal, the groups have filed a lawsuit in federal district court in Fresno, Calif., arguing that the state's rule that calls for a reduction in the carbon content of fuels sold in the state violates the U.S. Constitution and threatens the national market for ethanol. 

The rule calls for a 10-percent reduction in the carbon content of fuels sold in California by 2020.  

Ethanol producers have criticized the rule and its policies, arguing that it unfairly discriminates against corn-based ethanol because the measure takes into account land-use changes expected to occur worldwide if the U.S. starts growing corn primarily for fuel instead of for food. 

In a written statement, the two ethanol industry groups said California's low-carbon fuel standard would place "new regulatory obstacles" to ethanol and hamper a 2007 federal law that set targets for the U.S. to blend 36 billion gallons of biofuels a year into the nation's fuel supply in 2022 -- up from 11.1 billion gallons in 2009. The groups conclude that the California policy violates the Supremacy Clause of the U.S. Constitution because it hinders the goals of the 2007 federal law. 

California Air Resources Board officials, however, have expressed confidence in the rule's constitutionality, the Wall Street Journal reported.