From an article by John Dean at Findlaw:
Recently, the White House acknowledged that President Bush is talking with, and considering hiring, a non-government attorney, James E. Sharp. Sharp is being consulted, and may be retained, regarding the current grand jury investigation of the leak revealing the identity of Valerie Plame as a CIA covert operative.... Readers may wonder, why is Bush going to an outside counsel, when numerous government attorneys are available to him - for instance, in the White House Counsel's Office? The answer is that the President has likely been told it would be risky to talk to his White House lawyers, particularly if he knows more than he claims publicly.
And from Raw Story:
Sharp long has cloaked himself in secrecy, even taking the unusual move of paying to have his address and telephone number removed from the major Martindale legal directory. He was an assistant district attorney before he came to Washington and has a history of taking on cases with political implications. Sharp’s highest profile client was Maj. Gen. Richard V. Secord, a major figure in the Iran-Contra scandal who helped Lt. Col. Oliver North accumulate untaxed wealth in overseas accounts.