James 2:8 If ye fulfil the royal law according to the scripture, Thou shalt love thy neighbour as thyself, ye do well:
James came closer than the other writers to saying the law of love. I wish someone had, so that it would become clear that love rules our actions. When asked what is the greatest commandment Jesus answered love God and the second is like the first, love one another.
Colossians 3:14-16 (ESV) And above all these put on love, which binds everything together in perfect harmony. And let the peace of Christ rule in your hearts, to which indeed you were called in one body. And be thankful. Let the word of Christ dwell in you richly, teaching and admonishing one another in all wisdom, singing psalms and hymns and spiritual songs, with thankfulness in your hearts to God.
Paul hints of it strongly here in Colossians without coming right out and calling it the law of love. I know that many will resist putting the words love and law together because they enjoy this new found freedom in Christ but we are set free from sin, not love.
Let me try to explain my point in this way. There are natural laws and manmade laws. Take the law of gravity as an example. Gravity can be overcome with effort. Planes fly expending great amounts of fuel. Rockets lift man to great heights where gravity has the least amount of effect, but it still exists. Orbits deteriorate and satellites fall, gravity is still the law.
God is love and He dwells in your heart and that love never changes. Agape love acts in a predictable, consistent manner, and never stops being perfect in performance. Because His love is gentle we can overcome it with much less effort than it takes to overcome gravity.
The more effort we put into overcoming agape love the less and less its influence is felt until we get so lofty that it does not appear to be in us at all.