In front of my former apartment complex there in a break in the cement highway divider that allows traffic coming up the hill to pull over, cross two lanes of oncoming traffic and enter the complex. It is a scary maneuver. There isn't much room set aside for a turning lane and often the last few cars in line are actually blocking the cars coming up the hill that want to go straight through. Then there is the flow of traffic coming down the hill at breakneck speed. Finding a break in traffic big enough to allow a driver to safely cross the highway, is sometimes a challenge. There have been a few accidents, but nothing like the crashes and near misses caused by the cars trying to reverse the process.

Picture this: a driver leaving the complex wants to go up the hill but doesn't want to make a right hand turn, go down the hill, use the turn around at the bottom, and then come back up the hill past the same building he just left. So instead, he cuts across two lanes of traffic and uses the break in the barrier as his shortcut up the hill. If there is a lot of traffic, or people trying to turn into the complex, he blocks them. At worst he causes an accident. 

So a sign was put up to advise drivers that it is illegal to take the shortcut from the complex, across the lanes coming down the hill, and block traffic making the legal turn or coming up the hill.

Does everyone obey the sign? No, there are still stupid drivers who won't get the message until "crunch" time. However they can't claim ignorance and they know what the law is and what the consequences are for breaking it.

God's law, says Paul, is like that sign post. It tells us what to do and what not to do—what God's standards are. Can we keep those standards? Unlike the drivers who obey the sign to make make an illegal turn, we don't have a chance of keeping God's Law. So Paul rightly says, we can't be saved by the Law since we can't keep it. 

However, if we have no clue as to what God's standards are, we would never know how short we fall from them. If we have no idea that we have done anything that offends Him because we are ignorant of His standards, then we would hardly look for a way to solve the sin problem—which is what the Scriptures call the offenses we commit when we break God's Law. 

If we don't know what sin is and aren't moved by the Spirit to seek a remedy for it, we would not understand our need of a Saviour, or look for Him. The presence of the standard is indispensable to our search for a Saviour.

When Paul wrote the letter to the Romans, he very specifically noted that even without the Law, which was initially a "Jewish thing," those who didn't have the Law—the Gentiles—shouldn't think they were off the hook. God has revealed Himself in other ways so that, as Paul writes: "men are without excuse" (Romans 20). The image of God that is contained in us, that spiritual conscience that He breathed into mankind at creation, knows the emptiness that only God can fill. 

Obeying the signs doesn't justify me because my sinful self can't obey perfectly. But their presence tells me that if I am to escape the consequences of my failure, my sin, I need to seek the remedy that He has supplied: "But now a righteousness from God, apart from the law, has been made known, to which the Law and the prophets testify. This righteousness from God comes through faith in Jesus Christ to all who believe. There is no difference, for all have sinned and fall short of the glory of God, and are justified freely by his grace through the redemption that came by Christ Jesus. God presented him as a sacrifice of atonement through faith in his blood" (Romans 3:21-25a).

Where, before he came to Christ, the Law had condemned him to death, Paul says that now the Law serves as his signpost, indicating how he should live out this righteousness that God has gifted him with through faith in Christ (Romans 7, 8).

The sign in front of my apartment building has a two fold purpose—it condemns those who break it, it warns those who don't want to suffer the consequences of breaking it and want to live at peace with the authorities. It's a good thing that it exists.