The whole world is already in a personal relationship with God. Either one that is a curse, or one that is a blessing. This is what Paul is explaining in Romans 1 & especially Romans 2. The gentiles have the law written on their heart:
For all who have sinned without the law will also perish without the law, and all who have sinned under the law will be judged by the law.For it is not the hearers of the law who are righteous before God, but the doers of the law who will be justified. For when Gentiles, who do not have the law, by nature do what the law requires, they are a law to themselves, even though they do not have the law. They show that the work of the law is written on their hearts, while their conscience also bears witness, and their conflicting thoughts accuse or even excuse them on that day when, according to my gospel, God judges the secrets of men by Christ Jesus. -Romans 2:12-16
John Calvin notes that:
Now, as it is evident that the law of God which we call moral, is nothing else than the testimony of natural law, and of that conscience which God has engraven on the minds of men (Calvin, Institutes 4.20.16)
So we see that all those who are not Israelites, (which is basically everyone at this time) are still in a relationship with God, through the law written on the heart, where their consciences bear witness, either accusing or excusing them. They will be judged on that day also, and if we go on to Romans 3, it’s not good news…
He concludes that both Jews and Greeks (that’s synonymous with all gentiles, or everyone in the world) are under sin. (3:9) , and then in a quote of Psalm 36, he concludes that no one is righteous, no one seeks for God, no one does good, and among many other things they just don’t fear God. (3:10-18)
If there is any doubt that this is a blanket condemnation of the whole world, and that they will be judged by the moral law which is by nature written on their hearts, Paul concludes:
Now we know that whatever the law says it speaks to those who are under the law, so that every mouth may be stopped, and the whole world may be held accountable to God. For by works of the law no human being will be justified in his sight, since through the law comes knowledge of sin. -Romans 3:19-20
The whole world is held accountable, and by works of the law, no human being will be justified in God’s sight.
This is the covenant of works that we find in the Westminster Confession of Faith 7:1-2, and while there are some who say that all covenants that God establishes are gracious, it’s really confusing to say that.
Of course God doesn’t have to establish a covenant and promise blessings and eternal life based on the fulfillment of it, so yes, that is gracious of Him to do that for Adam and all his offspring, but at this point, the law is a curse to all Adam’s offspring. Paul calls the law a curse (Gal 3:10-14) , because as James notes it must be perfectly kept (James 2:10) to be any good to us. It must be perfectly and personally obeyed as our confession says (WCF 7:2) Does that sound like good news, or gracious? It sounds not only conditional, but like a curse, because we can’t meet the conditions of it and are all doomed to die a first and second death unless someone comes and fulfills it for us.
That is exactly what Christ came to do. He came to fulfill the law (Mat 5:17). He came to be born of a woman (so He could represent man) , born under the law (to perfectly keep it) to redeem those under the law, so that we might have eternal life, as adopted sons of God (Jn 3:16;Gal 4:4-5). We could sum it up like this: That Christ came to fulfill the covenant of works to save us in the covenant of grace through faith alone.
So everyone already is in a relationship with God. Both the covenant of works and the covenant of grace are still in place across both the OT and the NT. People are either in one or the other covenant. One is of grace, but the law is not of grace. Its promises are conditioned on the perfect personal fulfilment of the law. Perfectly loving God and neighbor. As Paul teaches in Romans 7:10. The very commandment that was intended to bring life, actually brought death. But thanks’ be to God for Jesus Christ our savior who fulfilled everything for us, and secured eternal life and the blessings of God for us who believe. Our relationship with God in Christ is all of grace, and we are family forever because of the work of Christ on our behalf in His obedient life and His atoning death. That’s all good news.