In
this Washington Times article, Charles Hunt claims "One of the most famous examples of warrantless searches in recent years was the investigation of CIA official Aldrich H. Ames, who ultimately pleaded guilty to spying for the former Soviet Union. That case was largely built upon secret searches of Ames' home and office in 1993, conducted without federal warrants."
Judd at Think Progress debunks the Hunt article here, but doesn't mention Ames specifically.
But this document from the Senate Select Committee on Intelligence clearly says that the search of Ames's home and office was conducted in compliance with FISA --
"Under applicable Attorney General guidelines, this meant that the FBI was able to seek authority under pertinent laws and Justice Department guidelines to employ a full array of investigative techniques against Ames. For instance, the Foreign Intelligence Surveillance Court issued orders authorizing electronic surveillance of Ames's office and residence."
It also says "The facts contained in the affidavit supporting the arrest and search warrants were summarized by representatives of the FBI."