Document ID: ./input/supremecourt_opinions/opinions/23pdf/22-451_7m58.pdf
Page Number: 86.0

Cite as:  603 U. S. ____ (2024) 

5 

KAGAN, J., dissenting 

parties  “decided  to  take  their  chances  with”  the  agency’s 
resolution.  Ibid.  Sometimes, though, the gaps or ambigui-
ties are what might be thought of as predictable accidents. 
They may be the result of sloppy drafting, a not infrequent 
legislative  occurrence.  Or  they  may  arise  from  the  well-
known limits of language or foresight.  Accord, ante, at 7, 
22.  “The subject matter” of a statutory provision may be too 
“specialized  and  varying”  to  “capture  in  its  every  detail.” 
Kisor, 588 U. S., at 566 (plurality opinion).  Or the provision 
may give rise, years or decades down the road, to an issue 
the enacting Congress could not have anticipated.  Which-
ever the case—whatever the reason—the result is to create 
uncertainty about some aspect of a provision’s meaning.

Consider  a  few  examples  from  the  caselaw.    They  will
help show what a  typical Chevron question looks like—or 
really, what a typical Chevron question is.  Because when 
choosing whether to send some class of questions mainly to 
a court, or mainly to an agency, abstract analysis can only 
go so far; indeed, it may obscure what matters most.  So I 
begin with the concrete: 

  Under  the  Public  Health  Service  Act,  the  Food  and 
Drug Administration (FDA) regulates “biological prod-
uct[s],”  including  “protein[s].”    42  U. S. C.  §262(i)(1). 
When  does  an  alpha  amino  acid  polymer  qualify  as 
such a “protein”?  Must it have a  specific, defined se-
quence  of  amino  acids?    See  Teva  Pharmaceuticals 
USA, Inc. v. FDA, 514 F. Supp. 3d 66, 79–80, 93–106 
(DC 2020). 

  Under the Endangered Species Act, the Fish and Wild-
life Service must designate endangered “vertebrate fish 
or wildlife” species, including “distinct population seg-
ment[s]”  of  those  species.    16  U. S. C.  §1532(16);  see 
§1533.  What makes one population segment “distinct” 
from another?  Must the Service treat the Washington
State population of western gray squirrels as “distinct”