Document ID: ./input/supremecourt_opinions/opinions/22pdf/21-454_4g15.pdf
Page Number: 13

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

7 

Opinion of the Court 

The  EPA  and  the  Corps  initially  promulgated  different
interpretations  of  “the  waters  of  the  United  States.”    The 
EPA defined its jurisdiction broadly to include, for example, 
intrastate lakes used by interstate travelers.  38 Fed. Reg. 
13529  (1973).  Conversely,  the  Corps,  consistent  with  its
historical authority to regulate obstructions to navigation,
asserted jurisdiction over only traditional navigable waters.
39 Fed. Reg. 12119 (1974).  But the Corps’ narrow definition 
did not last.  It soon promulgated new, much broader defi-
nitions designed to reach the outer limits of Congress’s com-
merce power.  See 42 Fed. Reg. 37144, and n. 2 (1977); 40 
Fed. Reg. 31324–31325 (1975).

Eventually the EPA and Corps settled on materially iden-
tical  definitions.    See  45  Fed.  Reg.  33424  (1980);  47  Fed.
Reg. 31810–31811 (1982).  These broad definitions encom-
passed “[a]ll . . . waters” that “could affect interstate or for-
eign commerce.”  40 CFR §230.3(s)(3) (2008).  So long as the 
potential for an interstate effect was present, the regulation 
extended the CWA to, for example, “intrastate lakes, rivers, 
streams (including intermittent streams), mudflats, sand-
flats,  wetlands,  sloughs,  prairie  potholes,  wet  meadows, 
playa lakes, or natural ponds.”  Ibid.  The agencies likewise
took an expansive view of the CWA’s coverage of wetlands
“adjacent” to covered waters.  §230.3(s)(7).  As noted, they
defined  “adjacent”  to  mean  “bordering,  contiguous,  or 
neighboring” and clarified that “adjacent” wetlands include 
those  that  are  separated  from  covered  waters  “by  man-
made  dikes  or  barriers,  natural  river  berms,  beach  dunes 
and  the  like.”  §230.3(b).  They  also  specified  that  “wet-
lands” is a technical term encompassing “those areas that
are inundated or saturated by surface or ground water at a
frequency and duration sufficient to support, and that un-
der  normal  conditions do  support,  a  prevalence  of  vegeta-
tion typically adapted for life in saturated soil conditions.”
§230.3(t).  The  Corps  released  what  would  become  a  143-
page manual to guide officers when they determine whether