Document ID: ./input/supremecourt_opinions/opinions/21pdf/20-1566_l5gm.pdf
Page Number: 10

Cite as:  596 U. S. ____ (2022) 

7 

Opinion of the Court 

substantive law.  And if that choice-of-law rule applies in
the  private-museum  suit,  so  too  it  must  apply  in  the  suit
here, against the Foundation.  That is the only way to en-
sure—as Section 1606 demands—that the Foundation, alt-
hough a Spanish instrumentality, will be liable in the same 
way as a private party.

In choosing instead to apply a federal choice-of-law rule, 
the  courts  below  could  well  have  created  a  mismatch  be-
tween the Foundation’s liability and a private defendant’s.
As  described  earlier,  those  courts  found  that  the  federal 
rule commanded the use of Spanish property law to deter-
mine Rue Saint-Honoré ’s rightful owner.  See supra, at 4. 
Spanish law (as the courts below understood it) made eve-
rything depend on whether, at the time of acquisition, the 
Foundation  knew  the  painting  was  stolen:  If  the  Founda-
tion  did  not  know—as  the  courts  in  fact  found—then  it 
owned the painting by virtue of possession.  See ECF Doc. 
No. 621, at 26–30, aff ’d, 824 Fed. Appx., at 454–455.  But 
now consider the possible result if the courts below had in-
stead applied California’s choice-of-law rule, as they would
have done in a private suit.  The Cassirer plaintiffs contend
that the California rule would lead to the application of Cal-
ifornia property law.  See Brief for Petitioners 13.  And they
argue that under California property law, even a good-faith 
purchaser  of  stolen  property  cannot  prevail  against  the 
rightful pre-theft owner.  See ibid.  We do not today decide
those  questions;  they  remain  in  the  hands  of  the  lower 
courts.  But if the Cassirers are right, the use of a federal 
choice-of-law rule in the courts below stopped Section 1606
from working: That rule led to the Foundation keeping the 
painting when a private museum would have had to give it 
back. 

And even were Section 1606 not so clear, we would likely 
reach the same result, because we see scant justification for 
federal common lawmaking in this context.  Judicial crea-
tion of federal common law to displace state-created rules