A prominent Washington businessman who is caught up in a campaign finance investigation is fighting to restrict the government’s ability to review tens of millions of pages of documents seized from his home and office.

Federal agents in March executed search warrants against Jeffrey Thompson, a longtime accountant and founding member of a professional services firm who is enmeshed in a probe over the 2010 mayoral election of Vincent Gray. Lawyers for Thompson, who has not been charged with a crime, want the U.S. Court of Appeals for the D.C. Circuit to limit the scope of the documents that investigators can review in the high-profile corruption probe.