Law is absolutely, eternally necessary. If you have a kingdom and are king of one person in your kingdom, anything goes, but the minute you add two people to your kingdom, you need LAW to keep men from cutting each other's heads off and stealing each others wives. Yes, the Law will make wise the simple. But it has an additional subtle purpose within it, it serves to show the degree of obedience (self-denial) his people will muster in love of the God behind it. Meditating upon it grows character in the soul and thanksgiving to God that such a wise judge could be at the center of the universe...gladness for the fact that we didn't end up with a despot sitting at the helm for all eternity.
Nonetheless, the Law does nothing for the emotional life of a person, which is where much of our life is lived from moment to moment, withIN the larger structure of law and order. Our emotions are tender things, reactionary things, at times seemingly helpless, responsive things, at other times unreasonable things, at times even wild things. At times overcome, dead. We see that our emotions need escorting, we need to lean upon the arm of a royal consort. The Law will not wrap its arms around us through suffering, will not comfort us, will not grant mercy, will not forgive us, will not walk with us through the valley of the shadow, will not help us sort out complex human interchanges, will not nudge us in morally high directions at grey areas/crossroads, will not delight us with miracles and surprises.
Are we only to obey the Law of God and find that the rest of our life dangles from a parachute? rides a roller coaster with no steadying hand? Are we to live life... loveless? Fortunately, we find that our wise God has covered all of that delicacy. The atonement has a face, extends an arm at every curb. A Person meets us where we hurt and is ever healing us. The atonement is lavish and reckless all-out bleeding, the ultimate squandering of personal love for another. We learn love by being shocked by encountering it.
And so we see that ever-erring and fragile beings need both divine law and divine mercy. Humans need to be guided by law, but nurtured by love. No wonder the scriptures say that "a throne is ESTABLISHED by love" (Proverbs 20:28). Potentates of the earth have come to realize that you can get to the throne by law, but you will only retain it by love.