From Wikedia:

In early January 2006, the New York Times, as part of its investigation into domestic surveillance by the National Security Agency, reported that Comey, who was Acting Attorney General during the March 2004 hospitalization of John Ashcroft, refused to certify the legality of central aspects of the NSA program. The certification was required under White House procedures in order for the program to continue.

After Comey's refusal, the newspaper reported, Andrew H. Card Jr., White House Chief of Staff, and Alberto R. Gonzales, then White House counsel and future Attorney General, made a visit to the George Washington University Hospital to attempt to win approval directly from Ashcroft for the program. According to the 2007 memoir of Jack Goldsmith, who had been head of the Office of Legal Counsel at the time, Comey went to the hospital to give Ashcroft support in withstanding pressure from the White House.