Document ID: ./input/supremecourt_opinions/opinions/23pdf/23a349_0813.pdf
Page Number: 41.0

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

19 

BARRETT, J., dissenting 

An agency must respond to “ ‘relevant’ and ‘significant’ pub-
lic comments,” and that requirement is not “particularly de-
manding”; the “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.’ ”  Public Citizen, Inc. v. 
FAA, 988 F. 2d 186, 197 (CADC 1993) (quoting Home Box 
Office, Inc. v. FCC, 567 F. 2d 9, 35, and n. 58 (CADC 1977); 
emphasis added); see §7607(d)(6)(B) (EPA must respond to 
“significant”  comments).    EPA  received  hundreds  of  com-
ments,  and  its  response  numbered  nearly  1,100  pages.  
Given the likelihood that the FIP’s emissions limits did not 
depend  on  the  covered  States,  the  risk  of  it  applying  to 
fewer  States  may  not  be  “important,”  and  comments  pur-
portedly raising that possibility might not be “relevant” and 
“significant.”  Moreover, the one comment that vaguely re-
ferred to a need for a “new assessment and modeling,” Air 
Stewardship  Comments  14,  was  “purely  speculative”  and 
“disclose[d]” no “factual or policy basis”; it likely merited no 
response, Home Box Office, 567 F. 2d, at 35, n. 58.  Requir-
ing more from EPA risks the “sort of unwarranted judicial 
examination  of  perceived  procedural  shortcomings”  that 
might “seriously interfere with that process prescribed by 
Congress.”  Vermont Yankee Nuclear Power Corp. v. Natu-
ral  Resources  Defense  Council,  Inc.,  435  U. S.  519,  548 
(1978).11 

C 
  Applicants face one more impediment: the Clean Air Act’s 
stringent harmless-error rule.  A court “reviewing alleged 
procedural errors . . . may invalidate [an EPA] rule only if 

—————— 

11 Despite the Court’s suggestion of forfeiture, ante, at 17, EPA could 
not have forfeited the argument that the comments the Court cites were 
too insubstantial to merit a response.  The Court relies on comments that 
were not raised until the applicants’ reply briefs or that were uncovered 
later by the Court itself.  See, e.g., Reply Brief in No. 23A351, p. 11 (rais-
ing the Air Stewardship Coalition “modeling” comment for the first time).