Sec. 162. (a) Upon the enactment of this part, all - 
       (1) international parks,
       (2) national wilderness areas  which exceed 5,000 acres in
     size,
       (3) national  memorial parks  which exceed 5,000  acres in
     size, and
  (4) national parks which exceed six thousand acres in size, and
which are in existence on the  date of enactment of the Clean Air
Act Amendments of 1977 shall be class I areas and may not  be re-
designated. All areas  which were redesignated  as class I  under
regulations promulgated  before such  date of enactment  shall be
class I areas which may be redesignated as provided in this part.
The extent of the areas designated as  Class I under this section
shall  conform to  any changes  in the  boundaries of  such areas
which  have occurred subsequent to  the date of  the enactment of
the  Clean Air  Act  Amendments  of  1977,  or  which  may  occur
subsequent to  the date  of the  enactment of  the Clean Air  Act
Amendments of 1990.
  (b)  All  areas in  such State  designated pursuant  to section
107(d) as attainment or  unclassifiable which are not established
as  class I under subsection  (a) shall be  class II areas unless
redesignated under section 164.
[42 U.S.C. 7472]