Document ID: ./input/supremecourt_opinions/opinions/21pdf/20-1530_n758.pdf
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2 

WEST VIRGINIA v. EPA 

Opinion of the Court 

the air.  84 Stat. 1683, 42 U. S. C. §7411(a)(1).  That stand-
ard  may  be  different  for  new  and  existing  plants,  but  in 
each case it must reflect the “best system of emission reduc-
tion”  that  the  Agency  has  determined  to  be  “adequately 
demonstrated”  for  the  particular  category.  §§7411(a)(1),
(b)(1), (d).  For existing plants, the States then implement 
that  requirement  by  issuing  rules  restricting  emissions 
from sources within their borders. 

Since passage of the Act 50 years ago, EPA has exercised 
this authority by setting performance standards based on 
measures that would reduce pollution by causing plants to
operate more cleanly.  In 2015, however, EPA issued a new 
rule concluding that the “best system of emission reduction”
for existing coal-fired power plants included a requirement
that such facilities reduce their own production of electric-
ity, or subsidize increased generation by natural gas, wind,
or solar sources. 

The question before us is whether this broader conception
of EPA’s authority is within the power granted to it by the 
Clean Air Act. 

I 
A 
The Clean Air Act establishes three main regulatory pro-
grams to control air pollution from stationary sources such
as power plants.  Clean Air Amendments of 1970, 84 Stat. 
1676,  42  U. S. C.  §7401  et seq.  One  program  is  the  New 
Source Performance Standards program of Section 111, at
issue  here.   The  other  two  are  the  National  Ambient  Air 
Quality  Standards  (NAAQS)  program,  set  out  in  Sections
108 through 110 of the Act, 42 U. S. C. §§7408–7410, and 
the  Hazardous  Air  Pollutants  (HAP)  program,  set  out  in 
Section 112, §7412.  To understand the place and function
of Section 111 in the statutory scheme, some background on 
the other two programs is in order.

The NAAQS program addresses air pollutants that “may