Gal 3:27 "For as many of you as have been baptized into Christ have put on Christ."
When one is baptized into Christ he "puts on Christ". The phrase "put one Christ' carries the idea of putting on a coat. When you put on a coat you are then IN the coat as when one puts on Christ he is then IN Christ.
The Greek word for "put on" is endyo meaning "to sink into (clothing), put on, clothe one's self" Strong's
So when one puts on Christ he then is "clothed" in Christ's glory, His perfect righteousness. Therefor falling out of Christ one falls out of His perfect righteousness.
Reformed theology teaches that the "righteousness of Christ" is credited to an individuals account via mental trust in the fact. Thus they use the term, "clothed in the righteousness of Christ."
By you using that term you are engaging them within their framework of error instead of pulling down the strongholds from the foundation. It is a fools errand to approach things that way.
The Bible verse you quoted does not say we are "clothed in the righteousness of Christ." It says...
Gal 3:27
For as many of you as have been baptized into Christ have put on Christ.
Gal 3:28
There is neither Jew nor Greek, there is neither bond nor free, there is neither male nor female: for ye are all one in Christ Jesus.
We have parallel passages like this...
Col 3:1 If ye then be risen with Christ, seek those things which are above, where Christ sitteth on the right hand of God.
Col 3:2 Set your affection on things above, not on things on the earth.
Col 3:3 For ye are dead, and your life is hid with Christ in God.
Col 3:4 When Christ, who is our life, shall appear, then shall ye also appear with him in glory.
Col 3:5 Mortify therefore your members which are upon the earth; fornication, uncleanness, inordinate affection, evil concupiscence, and covetousness, which is idolatry:
Col 3:6 For which things' sake the wrath of God cometh on the children of disobedience:
Col 3:7 In the which ye also walked some time, when ye lived in them.
Col 3:8 But now ye also put off all these; anger, wrath, malice, blasphemy, filthy communication out of your mouth.
Col 3:9 Lie not one to another, seeing that ye have put off the old man with his deeds;
Col 3:10
And have put on the new man, which is renewed in knowledge after the image of him that created him:
Col 3:11
Where there is neither Greek nor Jew, circumcision nor uncircumcision, Barbarian, Scythian, bond nor free: but Christ is all, and in all.
Col 3:12 Put on therefore, as the elect of God, holy and beloved, bowels of mercies, kindness, humbleness of mind, meekness, longsuffering;
Rom 6:4 Therefore
we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life.
Rom 6:5 For if we have been planted together in the likeness of his death, we shall be also in the likeness of his resurrection:
Rom 6:6 Knowing this, that our old man is crucified with him, that the body of sin might be destroyed, that henceforth we should not serve sin.
Rom 6:7 For he that is dead is freed from sin.
When you say, "
when one puts on Christ he then is "clothed" in Christ's glory, His perfect righteousness," all you are doing is twisting the passage you picked with rhetorical exposition in order to present a case from your own perceptions instead of letting the scripture actually speak.
You are approaching things within a theological framework developed by men and then applying that framework to the Bible. Sure you are not like these other people who are blatantly arguing in favour of being able to sin and not surely die, yet you are still operating from within the framework of the same error.
When we put on Christ it is in the context of abiding in a manifest state whereby God reckons our faith as righteousness. It has nothing to do with the righteousness of another cloaking you. By contending that it does you might as well adopt the Calvinist position because, in principle, your position is not much different.