OP, I assume you are referring to the natural law written by God in the conscience of every person.
In his encyclical Quanto Conficiamur Moerore of 10 August, 1863, Pius IX addressed the Italian bishops:
“It is known to us and to you that those who are in
invincible ignorance of our most holy religion, but who observe carefully the
natural law, and the precepts graven by God upon the hearts of all men, and who being disposed to obey God lead an honest and upright life, may, aided by the light of divine grace,
attain to eternal life; for God who sees clearly, searches and knows the heart, the disposition, the thoughts and intentions of each, in His supreme mercy and goodness by no means permits that anyone suffer eternal punishment, who has not of his own free will fallen into sin.”
As you can see, natural law may enable a person to “attain to eternal life” if it is truly followed. Do you have difficulty understanding the effect this has on one’s conscience? Maybe the CCC from the
Vatican website will help clarify it for you, beginning with the first article.
1776 “Deep within his conscience man discovers a law which he has not laid upon himself but which he must obey. Its voice, ever calling him to love and to do what is good and to avoid evil, sounds in his heart at the right moment. . . .** For man has in his heart a law inscribed by God.** . . . His conscience is man’s most secret core and his sanctuary. There he is alone with God whose voice echoes in his depths.”