On Friday, December 2, 2011, the International Swaps and Derivatives Association (ISDA) and the Securities Industry and Financial Markets Association (SIFMA) jointly filed a complaint in the U.S. District Court for the District of Columbia against the Commodity Futures Trading Commission (CFTC).  Their complaint challenges the final rules adopted by the CFTC at its October 18, 2011 meeting establishing speculative position limits on 28 commodity futures, option contracts and economically equivalent commodity swaps (the Position Limit Rules).  This article summarizes the Position Limit Rules and the lawsuit challenging them.  For hedge fund managers that trade covered commodities or derivatives based on them, the Position Limit Rules and the lawsuit can directly affect trading volumes and strategies.  See also “Recent CFTC Settlement with Former Moore Capital Trader Illustrates a Number of Best Compliance Practices for Hedge Fund Managers that Trade Commodity Futures Contracts,” Hedge Fund Law Report, Vol. 4, No. 30 (Sep. 1, 2011).