Document ID: ./input/supremecourt_opinions/opinions/06pdf/05-1120.pdf
Page Number: 33

Cite as:  549 U. S. ____ (2007) 

27 

Opinion of the Court 

postenactment  congressional  actions  and  deliberations  it 
views  as  tantamount  to  a  congressional  command  to  re-
frain  from  regulating  greenhouse  gas  emissions.    Even  if 
such postenactment legislative history could shed light on 
the  meaning  of  an  otherwise-unambiguous  statute,  EPA 
never identifies any action remotely suggesting that Con-
gress meant to curtail its power to treat greenhouse gases 
as  air  pollutants.    That  subsequent  Congresses  have  es-
chewed  enacting  binding  emissions  limitations  to  combat 
global  warming  tells  us  nothing  about  what  Congress 
meant  when  it  amended  §202(a)(1)  in  1970  and  1977.27 
And  unlike  EPA,  we  have  no  difficulty  reconciling  Con-
gress’ various efforts to promote interagency collaboration 
and  research  to  better  understand  climate  change28  with 
the  agency’s  pre-existing  mandate  to  regulate  “any  air 
pollutant”  that  may  endanger  the  public  welfare.    See  42 
U. S. C.  §7601(a)(1).    Collaboration  and  research  do  not 

—————— 

27 See  United  States v.  Price, 361  U. S.  304,  313  (1960)  (holding  that 
“the  views  of  a  subsequent  Congress  form  a  hazardous  basis  for  infer-
ring the intent of an earlier one”); see also Cobell v. Norton, 428 F. 3d 
1070,  1075  (CADC  2005)  (“[P]ost-enactment  legislative  history  is  not
only oxymoronic but inherently entitled to little weight”). 

28 See, e.g., National Climate Program Act, §5, 92 Stat. 601, 15 U. S. C. 
§2901  et  seq.  (calling  for  the  establishment  of  a  National  Climate
Program  and  for  additional  climate  change  research);  Global  Climate 
Protection Act of 1987, §1103, 101 Stat. 1408–1409 (directing EPA and
the Secretary of State to “jointly” develop a “coordinated national policy 
on  global  climate  change”  and  report  to  Congress);  Global  Change 
Research  Act  of  1990,  Tit.  I,  104  Stat.  3097,  15  U. S. C.  §§2921–2938
(establishing for the “development and coordination of a comprehensive 
and  integrated  United  States  research  program”  to  aid  in  “under-
stand[ing] 
. . .  human-induced  and  natural  processes  of  climate 
change”);  Global  Climate  Change  Prevention  Act  of  1990,  104  Stat.
4058,  7  U. S. C.  §6701  et  seq.  (directing  the  Dept.  of  Agriculture  to
study the effects of climate change on forestry and agriculture); Energy
Policy  Act  of  1992,  §§1601–1609,  106  Stat.  2999,  42  U. S. C.  §§13381–
13388  (requiring  the  Secretary  of  Energy  to  report  on  information 
pertaining to climate change).