items with the effect of +stat 'In Areas outside own nation's Control" will only take effect when during conquest, the nation you currently are allied to is not in control of the area you are in. This effect will take place in all zones within an area. This even applies to the actual cities of Windurst, San d'Oria, and Bastok.
For example: If you are currently allied to Windurst, and Bastok or San d'Oria controls the area of Elshimo Lowlands, then the effect of any armor's effects with 'In areas outside own nation's control' will be in place in Kazham, Norg, Sea Serpent Grotto, and Yuhtunga Jungle. Zoning into any of the areas will cause the effect to activate immediately.
Note that in order to obtain the benefits, you must have either Signet, Sanction or Sigil active. Further, these benefits will always activate in Lumoria (Sea), Dynamis, Limbus and Promyvion, as long as Signet/Sanction/Sigil is active. These benefits will never activate in Aht Urhgan areas. They do however, work in Beastmen controlled areas.