Document ID: ./input/supremecourt_opinions/opinions/21pdf/20-1530_n758.pdf
Page Number: 36.0

30 

WEST VIRGINIA v. EPA 

Opinion of the Court 

NAAQS.  It is quite another to simply authorize EPA to set 
the cap itself wherever the Agency sees fit.

Second, Congress added the above authorizations for the 
use  of  emissions  trading  programs  in  1990,  simultaneous 
with amending Section 111 to its present form.  At the time, 
cap-and-trade was a novel and highly touted concept.  The 
Acid  Rain  program  was  “the  nation’s  first-ever  emissions 
trading program.”  L. Heinzerling & R. Steinzor, A Perfect 
Storm:  Mercury  and  the  Bush  Administration,  34  Env.
L. Rep. 10297, 10309 (2004).  And Congress went out of its
way to amend the NAAQS statute to make absolutely clear 
that the “measures, means, [and] techniques” States could 
use 
included  cap-and-trade.
§7410(a)(2)(A).  Yet “not a peep was heard from Congress 
about  the  possibility  that  a  trading  regime  could  be  in-
stalled under §111.”  Id., at 10309. 

the  NAAQS 

to  meet 

Finally,  the  Government  notes  that  other  parts  of  the
Clean Air Act, past and present, have “explicitly limited the
permissible  components  of  a  particular  ‘system’ ”  of  emis-
sion reduction in some regard.  Brief for Federal Respond-
ents 32.  For instance, a separate section of the statute em-
powers EPA to require the “degree of reduction achievable 
through the retrofit application of the best system of contin-
uous  emission  reduction.”  §7651f(b)(2)  (emphasis  added).
The comparatively unadorned use of the phrase “best sys-
tem of emission reduction” in Section 111, the Government 
urges,  “suggest[s]  a  conscious  congressional” choice  not  to 
limit the measures that may constitute the BSER to those 
applicable at or to an individual source.  Id., at 32. 

These arguments, however, concern an interpretive ques-
tion  that  is  not  at  issue.    We  have  no  occasion  to  decide 
whether  the  statutory  phrase  “system  of  emission  reduc-
tion” refers exclusively to measures that improve the pollu-
tion performance of individual sources, such that all other 
actions are ineligible to qualify as the BSER.  To be sure, it 
is pertinent to our analysis that EPA has acted consistent