In the case of Mackay v. Uinta Development Co. (219 Fed. 116 (8th Cir. 1914)), Mackay
sent his sheep across privately-owned land on their way to some Federal land.
They ate all the grass, damaging the land. The owner of the land (Uinta) sued
for damages from the trespass. However, the Appellate Court found for Mackay.
The Court looked to Buford
v. Houtz (133 U.S. 320 (1890)) and found
that since Congress allows people to trespass on Federal land, there is an
implied license that people can graze their animals there.
The Court then extended the
doctrine to say that there is an implied license for a private person to
send their animals across private lands in order to get to public lands.
Since there was no way
Mackay could not have gotten his sheep to the public land without going
over private land, Congress must have meant it was legal to do so, right?
The Court found that if
Uinta wanted to keep sheep off their land, they would have to build a
fence.
That was a change from
English common-law (and followed in the eastern US), that it was the
livestock owner who had the responsibility from keeping his livestock
from straying, not the property owner.
Compare this case to Leo
Sheep Co. v. United States (440 U.S.
668 (1979)), which held that the Federal government does not
have a similar right of way.