You need to go back somewhat to ear lier in the chapter to get some context...
KJV Ephesians 4
Live as God's People
17 This I say therefore, and testify in the Lord, that ye henceforth walk not as other Gentiles walk, in the vanity of their mind,
18 Having the understanding darkened, being alienated from the life of God through the ignorance that is in them, because of the blindness of their heart:
19 Who being past feeling have given themselves over unto lasciviousness, to work all uncleanness with greediness.
20 But ye have not so learned Christ;
Notice what Paul is saying here. Don't walk as the gentiles walk... alienated from the life of God. Then he went on to describe all the things that characterise a life that separates someone from God. Lying, stealing etc etc etc. Paul is saying that Christians who practice such things are no different from unbelievers. They are not "saved". Paul is telling believers that they must put that life behind them. He wasn't giving them a choice... He quoted several of the commandments and several things Jesus spoke of in his sermons. A life of sin cancels any profession of belief.