You may also be interested in this anomaly of the American
Inventors' Protection Act of 1999, aka P.L. 106-113, by which 
sections 311-318 were added to 35 USC.  The Public Law includes  
a provision that lacks any mention of how it is to be
incorporated into 35 USC.  Still, this section (4607) is
part of a law passed by Congress and signed by the President,
so it IS the law.
         "SEC. 4607. ESTOPPEL EFFECT OF REEXAMINATION.
          "Any party who requests an inter partes reexamination under
section 311 of title 35, United States Code, is estopped from challenging at
a later time, in any civil action, any FACT determined during the process of
such reexamination, except with respect to a fact determination later proved
to be erroneous based on information unavailable at the time of the inter
partes reexamination decision. If this section is held to be unenforceable,
the enforceability of the remainder of this subtitle or of this title shall
not be denied as a result."
(emphasis by ALL CAPS is mine - RJM)

See also 65 FR 76756, 76765 (or word search 4607) (12/7/2000),
in which a commenter to the proposed rules on inter
partes examination proposed that a sentence be added to Rule 923 
to the effect that the denial of
a reexamination request would not be considered a finding of fact
under Section 4607.  The PTO's response was that it would be up to
the courts to decide what was a FACT for 4607 purposes.
It refused to add the sentence.