ORIGINAL: Froonp
Well, I think that Mziln's way is the best way to have a sound solution.
ORIGINAL: Frederyck
Well, if Eastern Poland is considered a Territory, Polish troops will not be able to use Brest-Litovsk or Lvov as primary supply sources. Heck, they wouldn't even be secondary supply sources for the poor Poles... I don't think this would be a good idea.
Eastern Poland only exist once the Russians enter it (and so, create it). This is similar for Bessarabia, who does not exist as a WiF entity before the Russians enter it, and make it part of Russia.
This was discussed again recently on the WiF list and although I agree it could use clarification and may well be unintended by the designers, the present rules in RAW do provide the answers.
1. East Poland is part of Poland (nothing else having been specified in RAW) and so it can be subject to partisans.
2. Russians don't count for the anti-partisan garrison because the CW must be the controller of the partisan and per RAW: "A unit has a garrison value only if it is face-up and not in the ZOC of an enemy unit. The unit must also be on the opposite side to the major power that will control the partisan."
3. Thus the partisan can be placed in East Poland,
but cannot go inside the Nazi-Soviet pact area because per RAW neutrality pacts: "After you enter into a neutrality pact with a major power, units controlled by other major powers on your side cannot enter hexes that are part of your common border with that major power if they are at war with that other major power."
4. The CW is placing the partisan and RAW says that: "The controlling major power can place a partisan unit in any enemy controlled hex in its country that is not in an enemy ZOC. If there are no such hexes, put the partisan back into the force pool." It also says: "Partisans are always at war with the conquering major power (and it's aligned minors) even if the partisan's controlling major power is not at war with the conquerer." This last quote proves that the "enemy controlled hexes" are relative to the partisan - not to the CW.
So we may not like it, but RAW allows it.