Document ID: ./input/supremecourt_opinions/opinions/06pdf/05-1120.pdf
Page Number: 16.0

10 

MASSACHUSETTS v. EPA 

Opinion of the Court 

cise that authority.  The agency began by recognizing that 
the  concentration  of  greenhouse  gases  has  dramatically
increased as a result of human activities, and acknowledged
the  attendant  increase  in  global  surface  air  temperatures. 
Id.,  at  52930.    EPA  nevertheless  gave  controlling  impor-
tance  to  the  NRC  Report’s  statement  that  a  causal  link
between  the  two  “ ‘cannot  be  unequivocally  established.’ ”  
Ibid. (quoting NRC Report 17).  Given that residual uncer-
tainty,  EPA  concluded  that  regulating  greenhouse  gas 
emissions would be unwise.  68 Fed. Reg. 52930. 

The  agency  furthermore  characterized  any  EPA  regula-
tion of motor-vehicle emissions as a “piecemeal approach” to
climate change, id., at 52931, and stated that such regula-
tion  would  conflict  with  the  President’s  “comprehensive 
approach”  to  the  problem,  id.,  at  52932.    That  approach 
involves additional support for technological innovation, the 
creation of nonregulatory programs to encourage voluntary
private-sector reductions in greenhouse gas emissions, and 
further research on climate change—not actual regulation. 
Id.,  at  52932–52933.    According  to  EPA,  unilateral  EPA 
regulation of motor-vehicle greenhouse gas emissions might 
also  hamper  the  President’s  ability  to  persuade  key  devel-
oping countries to reduce greenhouse gas emissions.  Id., at 
52931. 

III 

Petitioners,  now  joined  by  intervenor  States  and  local 
governments,  sought  review  of  EPA’s  order  in  the  United 
States  Court  of  Appeals  for  the  District  of  Columbia  Cir-
cuit.16  Although  each  of  the  three  judges  on  the  panel
wrote a separate opinion, two judges agreed “that the EPA 

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16 See  42  U. S. C.  §7607(b)(1)  (“A  petition  for  review  of  action  of  the 
Administrator in promulgating any . . . standard under section 7521 of 
this  title  . . .  or  final  action  taken,  by  the  Administrator  under  this
chapter may be filed only in the United States Court of Appeals for the 
District of Columbia”).