7.2.3.3.1: New
depots as part of a supply chain may not be placed in a minor neutral
unless the major power is at war with the neutral and may only be placed
in the territory of another major power if given access permission by, at
war with, or having imposed victory condition C.5 (see
4.5.2) on that major power.
[ 12.4 ] * PEACE TREATY LIMITED ACCESS: This option supersedes the
force repatriation rules in 4.4.6.2
and forces are not repatriated when peace is made. Instead, when peace is
made, the former enemies have a period of automatic "limited
access" to get their forces out of the former enemy power's
territory. 12.4.1 GARRISONS: By the end of three Land Phases after peace is
made, all garrison factors must be out of the other major power's cities.
In the case of a victor that chose peace condition C.5, the requirement
is reduced to getting garrisons out of the capital cities during this
period. 12.4.2 CORPS, FLEETS AND DEPOTS: By the end of six Land Phases
after peace is made, all corps, fleets, depots and depot garrison factors
must be out of the other major power's territory.
If we accept that this access grants permission to add new depots and not
just to remove them, then you could build depots in an enemy territory so
long as they are gone by the end of 6 months.