The Law of the Gospel requires us to make the decisive choice between "the two ways" and to put into practice the words of the Lord. It is summed up in the Golden Rule, "Whatever you wish that men would do to you, do so to them; this is the law and the prophets."
The entire Law of the Gospel is contained in the "new commandment" of Jesus, to love one another as he has loved us.
Source: Catechism of the Catholic Church (Vatican.va)