This action seems hypocritical of a government that claims to be pro free market. Sadly, it is being decided in the courts. Congress should pass legislation that may be bad for U.S. investment banks in the short-run, but will help allow the U.S. to hold on to its position as the world's largest capital market in the long-run.
Any action to disrupt the anti-trust exemption would hurt the earnings of all global investment banks that underwrite IPOs in the U.S. However, I don't think this cartel will be disrupted anytime soon. Even if U.S. IPO fees fell, the largest U.S. investment banks have very diverse earnings mixes that include trading, bonds, asset management, individual brokerage, private equity and hedge fund services.
Among the largest U.S. investment banks and IPO underwriters are Goldman Sachs (NYSE:GS), Morgan Stanley (NYSE:MS), Merril Lynch (MER), Lehman Brothers (LEH) and Citigroup (NYSE:C), JPMorgan Chase (NYSE:JPM).