The giving of a law by any competent authority implies the ability of the recipient to keep that law. The giving of a law presupposes the possibility of its violation, and, hence, a law always has penalties attached to it.
Father Adam was created in the image of God. When he sinned, he received a sentence or curse because of his disobedience to the divine will. Thus, a law must have been given him that was sufficiently explicit.
We are distinctly told that the sin of Eden was disobedience to a divine command. The justice of the death sentence upon Adam implied his comprehension of the law. He knowingly transgressed it. Otherwise, the fault would have been with the lawgiver. Adam was in a condition to receive the divine Law and to obey it. As a result of the violation, the full penalty came upon him.
We have no record that God presented a code of laws written in stone to Adam and Eve. A codification of laws is necessary today because of human weaknesses. But how could Adam possess a perfect law, under which he was tried and, through failure, condemned?
Laws do not need to be written externally – upon paper, stone, etc. The divine Law – an appreciation of right and wrong – was written within man’s perfect organism. In this manner God’s Law is within His own being and in all the angelic hosts. Thus, also, the divine Law was written in the very constitution of Adam and Eve. The Apostle Paul mentioned this in Romans 2:15, “the law (is) written in their hearts, their conscience also bearing witness.” Even over six thousand years after the fall, our hearts and minds still have an appreciation of justice and obedience.
Adam and Eve were not prone to sin. They were righteous, surrounded by righteous and perfect conditions, and conscious of their obligations to their Creator. They knew, not vaguely, but precisely, what he had commanded. They were, therefore, without excuse in their transgression.
Mercy might claim they had no experience involving the downward pains of sin and death. However, the fact that they did not fully comprehend the penalties does not excuse them. They knew the right course from the wrong one. The Apostle confirms the Genesis account saying that “Adam was not deceived.” (1 Timothy 2:14) Adam committed transgression knowingly, willfully, and he thus brought upon himself the curse, or sentence of willful sin. The penalty, which his Creator had previously declared, was death.