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Cite as:  598 U. S. ____ (2023) 

1 

Opinion of the Court 

NOTICE: This opinion is subject to formal revision before publication in the 
United  States  Reports.  Readers  are  requested  to  notify  the  Reporter  of 
Decisions,  Supreme  Court  of  the  United  States,  Washington,  D. C.  20543, 
pio@supremecourt.gov, of any typographical or other formal errors. 

SUPREME COURT OF THE UNITED STATES 

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No. 21–454 
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MICHAEL SACKETT, ET UX., PETITIONERS v. 
ENVIRONMENTAL PROTECTION 
AGENCY, ET AL. 

ON WRIT OF CERTIORARI TO THE UNITED STATES COURT OF 
APPEALS FOR THE NINTH CIRCUIT 

[May 25, 2023] 

JUSTICE ALITO delivered the opinion of the Court. 
This  case  concerns  a  nagging  question  about  the  outer 
reaches of the Clean Water Act (CWA), the principal federal 
law regulating water pollution in the United States.1  By all 
accounts, the Act has been a great success.  Before its en-
actment  in  1972,  many  of  the  Nation’s  rivers,  lakes,  and
streams were severely polluted, and existing federal legis-
lation had proved to be inadequate.  Today, many formerly
fetid bodies of water are safe for the use and enjoyment of 
the people of this country.

There is, however, an unfortunate footnote to this success 
story: the outer boundaries of the Act’s geographical reach 
have been uncertain from the start.  The Act applies to “the 
waters  of  the  United  States,”  but  what  does  that  phrase 
mean?  Does  the  term  encompass  any  backyard  that  is 
soggy  enough  for  some  minimum  period  of  time?    Does  it 
reach “mudflats, sandflats, wetlands, sloughs, prairie pot-
holes, wet meadows, [or] playa lakes?”2  How about ditches, 
swimming pools, and puddles? 
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1 86 Stat. 816, as amended, 33 U. S. C. §1251 et seq. 
2 40 CFR §230.3(s)(3) (2008).