...[I]nvestigators have uncovered even more accounting "irregularities" -- including overvaluation of assets, attempts to hide derivatives losses and the possible improper use of tax credits.... Which brings us to Mr. Oxley, the House Financial Services Chairman who is pressing a "reform" for Fannie and its sibling, Freddie Mac, that fails to address their core financial risks. His bill does nothing to reduce their huge portfolios of mortgage-backed securities (MBSs) and the derivatives they use to hedge those portfolios. Reducing their MBSs would dent their profitability. But a meltdown in their black-box hedging operations could have far worse consequences, and the...