Utah Power and Light Co. v. United States
243 U.S. 389 (1917)
UPLC built a power plant in a
National Forest in Utah.
They got permission from
Utah, but never bothered to ask the Federal government.
Once the Federal government
realized what happened, they sued for an injunction.
UPLC argued that they had
gotten permission from the State, and that should be good enough.
UPLC argued that Utah law
should apply because there had been no cession of jurisdiction by the
State under the Enclave Clause (Art.
1 §8, cl. 17). Therefore, the Federal government did not have
the right to preempt State law.
See Fort Leavenworth R.
Co. v. Lowe (114 U.S. 525 (1885))
for more info on how the Enclave Clause is applied.
The US Supreme Court found for
the US and granted the injunction.
The US Supreme Court found
that that if State law on Federal property conflicts with Federal law,
then the Property Clause (Article
IV, §3, cl. 2), and the Supremacy Clause (Article IV, §2) trump State
The Court didn't base their
decision on the Enclave Clause at
There aren't very many modern
cases regarding the Enclave Clause.
It is much more common for the Federal government invoke a combination of
the Property Clause and the Supremacy
Clause to keep the States from
regulating Federal land.
For example, see Kleppe
v. New Mexico (426 U.S. 529 (1976)).