Allahpundit says "We’re just swimming in “what if a Republican did it?” material" and he is right. These omissions are a big deal, though it is unclear if anything could come from it now. My understanding is that he was questioned on some of the brief he omitted which would tamper down on the 'this may have changed the outcome' on those.
"Attorney General Eric Holder didn’t tell the Senate Judiciary Committee about seven Supreme Court amicus briefs he prepared or supported, his office acknowledged in a letter Friday, including two urging the court to reject the Bush administration’s attempt to try Jose Padilla as an enemy combatant.
“It has come to our attention that some but not all briefs submitted to the Supreme Court by or on behalf of Attorney General Holder as counselor amicus were supplied to the Committee in the course of his confirmation process last year. We regret the omission,” Assistant Attorney General Ronald Weich wrote to Senate Judiciary Committee Chairman Patrick Leahy.
Weich supplied a list of seven briefs that White House lawyers missed when they prepared Holder’s confirmation questionnaire, in the cases Padilla v. Hanft, Johnson v. Bush, Miller-El v. Dretke, Rumsfeld v. Padilla, Dretke v. Haley, Missouri v. Seibert and McDonald v. United States. Holder was party to the amicus brief in all of the cases except McDonald v. United States, in which he was the lawyer who prepared the brief.
Holder’s questionnaire listed three: D.C. v. Heller, Miller-El v. Cockrell and a different brief in Johnson v. Bush."