The case is US v. Safavian, and the opinion is here.

From the news coverage:

WASHINGTON — A federal appeals court overturned the conviction of a former White House official Tuesday in a significant defeat for prosecutors who are overseeing the investigation into the Jack Abramoff influence-peddling scandal.

David Safavian was convicted in 2006 of four charges related to statements he made to officials who were investigating Abramoff, a former lobbyist who pleaded guilty to conspiring to bribe lawmakers and bilking his Indian-tribe clients out of millions of dollars.

The U.S. Court of Appeals for the District of Columbia Circuit threw out two felony-concealment charges against Safavian, saying he had “no legal duty to disclose” details about his relationship with Abramoff to General Services Administration ethics and inspector-general officials. At the time, Safavian was the GSA’s chief of staff and helped Abramoff attempt to buy two GSA-managed properties in the Washington area.