Quote from : Catechism of the Catholic Church Book

1951. Law is a rule of conduct enacted by competent authority for the sake of the common good. The moral law presupposes the rational order, established among creatures for their good and to serve their final end, by the power, wisdom, and goodness of the Creator. All law finds its first and ultimate truth in the eternal law. Law is declared and established by reason as a participation in the providence of the living God, Creator and Redeemer of all.