Nice try but, no cigar. Maybe you should be asking Janet Reno why she didn't prosecute Clinton.
Contempt of Congress is initiated by a resolution reported from the affected congressional committee which can cite any individual for contempt. The resolution must then be adopted by the House or Senate. If the relevant chamber adopts the contempt resolution recommended by one of its committees, the matter is referred to a U.S. Attorney for prosecution. The U.S. Attorney may call in a grand jury to decide whether or not to indict and prosecute. If prosecuted by the courts and found guilty of contempt, the punishment is presently set at up to one year in prison and/or up to $1,000 in fines.
Thanks to the fine folks at C-Span:
http://www.c-span.org/questions/weekly9.htm
So Janet Reno could not have prosecuted Clinton without a contempt resolution from Congress. (The last time that happened, by the way, was 1982).