Document ID: ./input/supremecourt_opinions/opinions/19pdf/19-715_febh.pdf
Page Number: 30.0

Cite as:  591 U. S. ____ (2020) 

5 

THOMAS, J., dissenting 

Constitution of the United States §1338, p. 210 (1833).  Re-
latedly,  the  Constitution  prohibits  ex  post  facto  laws,  §9, 
cl. 3, reinforcing the fact that Congress’ power to punish is 
limited.2    And  in  a  system  in  which  Congress  is  not  su-
preme, the individual protections in the Bill of Rights, such
as the prohibition on unreasonable searches and seizures, 
meaningfully  constrain  Congress’  power  to  compel  docu-
ments from private citizens.  Cf. 1 St. George Tucker, Black-
stone’s Commentaries 203–205, n. § (1803); see also D. Cur-
rie,  The  Constitution  in  Congress:  The  Federalist  Period,
1789–1801, p. 268 (1997). 
  Furthermore, Kilbourn—this Court’s first decision on the 
constitutionality  of  legislative  subpoenas—emphasized
that Parliament had  more powers than Congress.  There, 
the congressional respondents relied on Parliament’s inves-
tigatory power to support a legislative subpoena for testi-
mony and documents.  The Court rejected the analogy be-
cause  the  judicial  powers  of  the  House  of  Commons—the
lower house of Parliament—exceeded the judicial functions 
of the House of Representatives.  Kilbourn, supra, at 189. 
At bottom, Kilbourn recognized that legislative supremacy
was decisively rejected in the framing and ratification of our 
Constitution, which casts doubt on the Committees’ claim 
that they have power to issue legislative subpoenas to pri-
vate parties. 

B 
The  subpoenas  in  these  cases  also  cannot  be  justified
based  on  the  practices  of  18th-century  American  legisla-

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2 The Constitution also enumerates a limited set of congressional priv-
ileges.  Although I express no opinion on the question, at least one early
commentator thought the canon of expressio unius meant that Congress
had no unenumerated privileges, such as the power to hold nonmembers 
in contempt.  1 St. George Tucker, Blackstone’s Commentaries 200, n. §
(1803).