U.S. trade groups filed a lawsuit on Tuesday against the CFTC, challenging a recent rule requiring mutual funds to register with the agency.  The Investment Company Institute (ICI) and the U.S. Chamber of Commerce complained that the rule duplicates a requirement that funds register with the SEC. Filed in U.S. District Court for the District of Columbia, the complaint alleges that the CFTC did not properly weigh the costs and benefits of the rule before it was finalized in February.  It creates confusion, not clarity, according to a statement by David Hirschmann, head of the Chamber's Center for Capital Markets Competitiveness, "by subjecting mutual funds to redundant, overlapping, and unnecessary regulatory requirements.  The CFTC completely ignored its statutory duty to evaluate the costs this unnecessary regulation will undoubtedly impose on the economy." The ICI, a mutual fund industry trade group, warned the rule would cost investors, by imposing significant compliance costs on mutual fund advisers which, in turn, are charged to the shareholders. A CFTC spokesman had no immediate comment. These and other industry groups have begun playing "hardball" with regulators, challenging financial regulations issued in the aftermath of the 2007-2009 financial crisis.  Their main line of attack has been that regulators are not following requirements that they do thorough cost-benefit analyses before issuing final rules. Such a strategy was successful with a rule linked to the 2010 Dodd-Frank financial oversight law - a federal appeals court in July 2011 struck down the SEC's "proxy access" rule that would have made it easier for shareholders to nominate directors to corporate boards.  The SEC was chided for failing to adequately disclose the costs vs. benefits. In a separate matter, the CFTC is facing a legal challenge from SIFMA and the ISDA (Int'l Swaps and Derivatives Ass'n over a rule intended to curb speculation in commodities markets.  [Reuters, 4/17/12]