It’s not hard to be perplexed when trying to understand the U.S. Code (link to searchable versions) and the niceties of codification. Maybe this will help:
Lost Laws: What We Can’t Find In The U.S. Code, Legal Research Plus (blog), May 23, 2010, by Paul Lomio:
(Re Article: Lost Laws: What We Can’t Find In The U.S. Code, by Will Tress, Golden Gate University Law Review, Vol. 40, Issue #2, Winter 2010, p. 129) (SSRN direct link.)