Its might be worth noting that when he said that, the Temple at Jerusalem was still standing and would be for 30 or so years until 70 AD. As for "the Law":

And thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind, and with all thy strength: this is the first commandment. And the second is like, namely this, Thou shalt love thy neighbour as thyself. There is none other commandment greater than these. --Mark 12:30-31- (KJV)