"In reaching the charging decisions described in Volume 1... the Office determined whether the conduct it found amounted to a violation of federal criminal law chargeable under the Principles of Federal Prosecution. ...The standard set forth in the Justice Manual is whether the conduct constitutes a crime; if so, whether admissible evidence would probably be sufficient to obtain and sustain a conviction; and whether prosecution would serve a substantial federal interest that could not be adequately served by prosecution elsewhere or through non-criminal alternatives."