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Page Number: 9

6 

UNITED STATES v. WASHINGTON 

Opinion of the Court 

its face, the law applies only to a “person, including a con-
tractor  or  subcontractor,  who  was  engaged  in  the  perfor-
mance of work, either directly or indirectly, for the United
States.”  §51.32.187(1)(b).  The law thereby explicitly treats 
federal  workers  differently  than  state  or  private  workers. 
Cf. Dawson v. Steager, 586 U. S. ___, ___ (2019) (slip op., at 
6) (“Whether a State treats similarly situated state and fed-
eral employees differently depends on how the State has de-
fined the favored class”).  And, in doing so, the law imposes 
upon  the  Federal  Government  costs  that  state  or  private 
entities do not bear.  The law consequently violates the Su-
premacy Clause unless Congress has consented to such reg-
ulation through waiver. 

B 
We will find that Congress has authorized regulation that 
would  otherwise  violate  the  Federal  Government’s  inter-
governmental immunity “only when and to the extent there 
is a clear congressional mandate.”  Hancock v. Train, 426 
U. S.  167,  179  (1976)  (internal  quotation  marks  omitted). 
In other words, Congress must “provid[e] ‘clear and unam-
biguous’  authorization  for”  this  kind  of  state  regulation. 
Goodyear Atomic, 486 U. S., at 180 (quoting EPA v. Califor-
nia ex rel. State Water Resources Control Bd., 426 U. S. 200, 
211 (1976)).

Washington argues that Congress has provided such au-
thorization by waiving federal immunity from state work-
ers’ compensation laws on federal lands and projects.  The 
statutory  waiver  Washington  relies  upon,  40  U. S. C. 
§3172(a), says that “[t]he state authority charged with en-
forcing  and  requiring  compliance  with  the  state  workers’ 
compensation  laws  . . .  may  apply  [those]  laws  to  all  land
and premises in the State which the Federal Government 
owns,” as well as “to all projects, buildings, constructions,
improvements, and property in the State and belonging to
the Government, in the same way and to the same extent