PESCO was seen as the way to enable the common defence foreseen in Article 42, but the scepticism towards further integration that had arisen around the rejection of the European Constitution meant its activation was unlikely.
PESCO se smatrao načinom ostvarivanja ideje o zajedničkoj obrani predviđenoj člankom 42., ali skepticizam prema jačanju EU integracije nakon neuspjeha sa Europskim ustavom značio je da je njegova realizacija malo vjerojatna.