The Rule of Law in the Eternities

How could he sin if there was no law? How could there be a law save there was a punishment?

Now, there was a punishment affixed, and a just law given, which brought remorse of conscience unto man.

Now, if there was no law given--if a man murdered he should die--would he be afraid he would die if he should murder? 

And also, if there was no law given against sin men would not be afraid to sin.

And if there was no law given, if men sinned what could justice do, or mercy either, for they would have no claim upon the creature? 

But there is a law given, and a punishment affixed, and a repentance granted; which repentance, mercy claimeth; otherwise justice claimeth the creature and executeth the law, and the law inflicteth the punishment; if not so, the works of justice would be destroyed, and God would cease to be God.

Alma 42:17-23