Document ID: ./input/supremecourt_opinions/opinions/23pdf/23a349_0813.pdf
Page Number: 1.0

(Slip Opinion) 

OCTOBER  TERM,  2023 

1 

Syllabus 

NOTE:  Where  it  is  feasible,  a  syllabus  (headnote)  will  be  released,  as  is 
being  done  in  connection  with  this  case,  at  the  time  the  opinion  is  issued. 
The  syllabus  constitutes  no  part  of  the  opinion  of  the  Court  but  has  been 
prepared  by  the  Reporter  of  Decisions  for  the  convenience  of  the  reader. 
See United States v. Detroit Timber & Lumber Co., 200 U. S. 321, 337. 

SUPREME COURT OF THE UNITED STATES 

Syllabus 

OHIO ET AL v. ENVIRONMENTAL PROTECTION 
AGENCY ET AL 

ON APPLICATIONS FOR STAY 

No. 23A349.  Argued February 21, 2024—Decided June 27, 2024* 

The Clean Air Act envisions a collaborative effort between States and the 
federal government to regulate air quality.  When the Environmental 
Protection  Agency  sets  standards  for  common  air  pollutants,  States 
must submit a State Implementation Plan, or SIP, providing for the 
“implementation, maintenance, and enforcement” of those standards 
in their jurisdictions.  See 42 U. S. C. §7410(a)(1).  Because air currents 
can carry pollution across state borders, States must also design their 
plans with neighboring States in mind.  Under the Act’s “Good Neigh-
bor Provision,” state plans must prohibit emissions “in amounts which 
will . . . contribute significantly to nonattainment in, or interfere with 
maintenance by, any other State” of the relevant air-quality standard.  
§7410(a)(2)(D)(i)(I).    Only  if  a  SIP  fails  to  satisfy  the  “applicable  re-
quirements” of the Act may EPA issue a Federal Implementation Plan, 
or FIP, for the noncompliant State that fails to correct the deficiencies 
in its SIP.  §§7410(k)(3), (c)(1). 
  In 2015, EPA revised its air-quality standards for ozone, thus trig-
gering a requirement for States to submit new SIPs.  Years later, EPA 
announced its intention to disapprove over 20 SIPs because the agency 
believed they had failed to address adequately obligations under the 
Good Neighbor Provision.  During the public-comment period for the 
proposed SIP disapprovals, EPA issued a single proposed FIP to bind 

—————— 

* Together  with  No.  23A350,  Kinder  Morgan,  Inc.,  et al.  v.  Environ-
mental Protection Agency et al.; No. 23A351, American Forest & Paper 
Assn.  et al.  v.  Environmental  Protection  Agency,  No.  23A384,  United 
States Steel Corp. v. Environmental Protection Agency et al.,  also on ap-
plications for stay.