The
Insular Cases made the distinction between "Incorporated" territories
like Hawaii and Alaska (where full US sovereignty had been established),
and "unincorporated" territories (like Puerto Rico and the Philippines)
which came into US hands through war, but which were not claimed as
sovereign territory.
The Court said that the Constitution applies totally in the incorporated
areas, and only partially (meaning: basic due process rights) in the
unincorporated.