Document ID: ./input/supremecourt_opinions/opinions/23pdf/23a349_0813.pdf
Page Number: 3

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

3 

Syllabus 

EPA’s plan rested on an assumption that all the upwind States would 
adopt emissions-reduction measures up to a uniform level of costs to 
the  point of  diminishing  returns.    Commenters  posed  their  concerns 
that if upwind States fell out of the planned FIP, the point at which 
emissions-control  measures  maximize  cost-effective  downwind  air-
quality improvements might shift.  To this question, EPA offered no 
reasoned response.  As a result, the applicants are likely to prevail on 
their argument that EPA’s final rule was not “reasonably explained,” 
Prometheus  Radio  Project,  592  U. S.,  at  423,  and  that  it  instead  ig-
nored “an important aspect of the problem” before it, State Farm Mut. 
Automobile Ins. Co., 463 U. S., at 43.  Pp. 11–13. 

(c) EPA’s alternative arguments are unavailing.  First, EPA argues 
that adding a “severability” provision to its final rule—i.e., providing 
the  FIP  would  “continue  to  be  implemented”  without  regard  to  the 
number  of  States  remaining—responded  to  commenters’  concerns.  
But EPA’s response did not address those concerns so much as it side-
stepped them.  Nothing in the final rule’s severability provision actu-
ally addressed whether and how measures found to maximize cost-ef-
fectiveness  in  achieving  downwind  ozone  air-quality  improvements 
with the participation of all the upwind States remain so when many 
fewer States might be subject to the agency’s plan.  Second, EPA in-
sists that no one raised that concern during the public comment period.  
The  Act’s  “reasonable  specificity”  requirement,  however,  does  not 
mean a party must rehearse the identical argument made before the 
agency.  Here, EPA had notice of the objection, and its own statements 
and actions confirm the agency appreciated the concern.  Third, EPA 
argues that applicants must return to EPA and file a motion asking it 
to  reconsider  its  final  rule  before  presenting  their  objection  in  court 
because  the  “grounds  for  [their]  objection  arose  after  the  period  for 
public comment.”  §7607(d)(7)(B).  Nothing requires the applicants to 
return to EPA to raise (again) a concern EPA already had a chance to 
address.  Pp. 13–17. 

Applications for stay granted. 

  GORSUCH,  J.,  delivered  the  opinion  of  the  Court,  in  which  ROBERTS, 
C. J., and THOMAS, ALITO, and KAVANAUGH, JJ., joined.  BARRETT, J., filed 
a  dissenting  opinion,  in  which  SOTOMAYOR,  KAGAN,  and  JACKSON,  JJ., 
joined.