Romans 5:20

Continuing Romans, we have just been told that as one man's disobedience caused many to be sinners, even so one man's obedience can cause many to become righteous.

Moreover the law entered, that the offence might abound. But where sin abounded, grace did much more abound: 21 That as sin hath reigned unto death, even so might grace reign through righteousness unto eternal life by Jesus Christ our Lord. (Romans 5:20-21)

What does this mean? When there are no copyright laws, nobody pirates media, but they may not pay the producer and soon media would cease to innovate. As there are gradually more and more laws in our society it gets harder and harder to avoid breaking the law. But these laws are usually introduced for good reasons and although we technically commit more crimes our society is better as a whole because of it.
In the same way, when there are few moral laws, we would not break them very often. But since there are many such laws we all break them. But even if we did not break moral laws often it would not be helpful for us. We need many laws about right and wrong to help us see that we need the forgiveness of Jesus. When we have seen that we are very guilty, we come to Jesus for forgiveness and he gives us power to overcome these sins and love each other.
Therefore just as one man's sin brought us death, and one man's obedience brought us life: the law brings us remorse (~repentance) and Jesus brings us pardon and reform.
Without the law to bring remorse, it would be hard for us to feel the need for Jesus to pardon and reform us.

There is a side point I find interesting. That is the question of salvational issues. If many laws bring us greater remorse and lead to greater pardon and reformation, then it is pointless to talk about issues as being salvational or not. Every true law of God we know helps us to find salvation, though on its own it probably doesn't make much difference.