Document ID: ./input/supremecourt_opinions/opinions/23pdf/23a349_0813.pdf
Page Number: 33

Cite as:  603 U. S. ____ (2024) 

11 

BARRETT, J., dissenting 

cost-effectiveness thresholds and chosen emissions-control 
measures.4  That is not how EPA understood it.  EPA char-
acterized  this  comment  as  arguing  that  “by  taking  action 
before considering comments on the proposed disapprovals, 
the EPA is presupposing the outcome of its proposed rule-
makings on the SIPs.”  Response to Comments 147 (noting 
this comment’s ID number, 0518).  And EPA explained that 
it “disagree[d]” with the argument that the “sequence” of its 
actions  was “improper, unreasonable, or  bad  policy”;  EPA 
had a statutory obligation to promulgate a FIP by the Au-
gust  2024  NAAQS  attainment  deadline.    Id., at  150.    If  a 
commenter  had  said  with  reasonable  specificity  what  the 
Court  says  today—that  “a  different  set  of  States  might 
mean that the ‘knee in the curve’ might shift,” ante, at 7—
EPA  could  have  responded  with  more  explanation  of  why 
its  methodology  did  not  depend  on  the  number  of covered 
States—as  it  has  recently  explained.    But  EPA  cannot  be 
penalized if it did not have reasonable notice of this objec-
tion.5 

—————— 

4 So too with Portland Cement’s comment.  See ante, at 7.  That com-
ment simply echoes the quoted sentence from the Air Stewardship Coa-
lition almost word for word, also in the context of objecting to EPA’s de-
cision to propose a FIP before finalizing its SIP disapprovals.  Comments 
of Portland Cement Association 7 (June 21, 2022). 

5 The  Court  concludes  to  the  contrary  only  by  building  out  the  com-
ment’s bare reference to a “new assessment and modeling” with its own 
inferences about the possible effect of different numbers of States on “the 
math.”    Ante,  at  16,  n. 12  (internal  quotation  marks  omitted).    But  as 
explained above, the comment itself said nothing about States dropping 
out of the final plan or the possible impact of different numbers of States 
on the FIP’s cost thresholds or emissions limits.  It is hard to believe that 
a single sentence with no elaboration or explanation of the potential is-
sue—in a sea of thousands of pages of comments—gave EPA reasonable 
notice that it should have included in its final rule a detailed explanation 
of why the FIP’s emissions limits did not depend on the number of States.  
Cf.  Public  Citizen,  Inc.  v.  FAA,  988  F. 2d  186,  197  (CADC  1993)  (An 
“agency need not respond at all to comments that are ‘purely speculative 
and do not disclose the factual or policy basis on which they rest’ ”).