This is Eph 2:1-2, Catholic translation:
You were dead through the trespasses and sins 2 in which you once lived, following the course of this world, following the ruler of the power of the air, the spirit that is now at work among those who are disobedient.
Reading just those two verses suggests that the spirit that St Paul is talking about here is not the Holy Spirit, but the evil one under whose influence people lived before they believed in Jesus and accepted the faith. That same spirit is now at work in those who are disobedient - i.e. those who do not belong to Christ, but to the world and who do not keep the commandments.
When people live according to worldly principles or willingly persist in their sins, they open the way for the evil one to work (i.e. by willing rejecting the faith and the gift of sanctifying grace, they, by their own choice, cut themselves off from the victory of Christ over the evil one). Through our sins and disobedience we open the way for the evil one.
It cannot be that because of the action of the evil spirit we become disobedient since it wouldn't involve our free will and choice - so, the evil one can work as hard as he wants (and God permits him) - but we are not under his influence and he cannot make us disobey God, unless we fully consent to his temptations in full knowledge that the matter is against God's will (as expressed in the commandments and dictated by our conscience).