Document ID: ./input/supremecourt_opinions/opinions/19pdf/18-260_jifl.pdf
Page Number: 21.0

Cite as:  590 U. S. ____ (2020) 

17 

Opinion of the Court 

At  the  same  time,  courts  can  provide  guidance  through
decisions in individual cases.  The Circuits have tried to do 
so,  often  using  general  language  somewhat  similar  to  the
language we have used.  And the traditional common-law 
method,  making  decisions  that  provide  examples  that  in 
turn lead to ever more refined principles, is sometimes use-
ful, even in an era of statutes. 

The  underlying  statutory  objectives  also  provide  guid-
ance.  Decisions should not create serious risks either of un-
dermining  state  regulation  of  groundwater  or  of  creating
loopholes that undermine the statute’s basic federal regu-
latory objectives.

in  numerous  ways, 

EPA,  too,  can  provide  administrative  guidance  (within 
including
statutory  boundaries) 
through, for example, grants of individual permits, promul-
gation  of  general  permits,  or  the  development  of  general
rules.  Indeed, over the years, EPA and the States have of-
ten considered the Act’s application to discharges through
groundwater. 

Both Maui and the Government object that to subject dis-
charges  to  navigable  waters  through  groundwater  to  the
statute’s  permitting  requirements,  as  our  interpretation
will  sometimes  do,  would  vastly  expand  the  scope  of  the 
statute, perhaps requiring permits for each of the 650,000 
wells like petitioner’s or for each of the over 20 million sep-
tic systems used in many Americans’ homes.  Brief for Pe-
titioner  44–48;  Brief  for  United  States  as  Amicus  Curiae 
24–25.  Cf. Utility Air Regulatory Group v. EPA, 573 U. S. 
302, 324 (2014).

But  EPA  has  applied  the  permitting  provision  to  some 
(but not to all) discharges through groundwater for over 30 
years.  See  supra,  at  8–9.  In  that  time  we  have  seen  no 
evidence of unmanageable expansion.  EPA and the States 
also have tools to mitigate those harms, should they arise, 
by  (for  example)  developing  general  permits  for  recurring
situations  or  by  issuing  permits  based  on  best  practices