there is certainly sin without law -
Romans 5:13
For until the law sin was in the world, but sin is not imputed when there is no law.
But in Exodus 16 He gave them for the first time a sabbath law, telling them not to gather manna in the 7th day. this He did to prove their disobedience -
Exodus 16:4
Behold, I will rain bread from heaven for you. And the people shall go out and gather a certain quota every day, that I may test them, whether they will walk in My law or not.
a test they failed:
Exodus 16:20
Notwithstanding they did not heed Moses. But some of them left part of it until morning, and it bred worms and stank. And Moses was angry with them.
which is no surprise, because they had been complaining against the LORD from the day He brought them out of Egypt, accusing Him of saving them only in order to kill them in the wilderness. in fact even this chapter opens with their wicked accusations:
Exodus 16:2-3
Then the whole congregation of the children of Israel complained against Moses and Aaron in the wilderness. And the children of Israel said to them,
"Oh, that we had died by the hand of the LORD in the land of Egypt, when we sat by the pots of meat and when we ate bread to the full! For you have brought us out into this wilderness to kill this whole assembly with hunger."
so Exodus 20 and the rest of the Torah is a law for a disobedient and unbelieving people, as scripture witnesses:
1 Timothy 1:9
the law is not made for a righteous person, but for the lawless and insubordinate, for the ungodly and for sinners, for the unholy and profane...
so then if we have died with Christ and His righteousness is attributed to us through faith, by His atonement, why would God give the righteous a ministry of death engraved in stone? does He not give us instead a ministry of life?
to us He said, "love one another as I have loved you" and He said, "whoever believes has eternal life" - - but to the unbelieving and disobedient, who accuse God of murder, having no faith even though they see the Son in a pillar of fire before them, He said "do this and live"
for them Aaron continuously shed blood to cover their sins - but for us, Christ died once and for all.
we are not opposed to the righteousness of the Law, but it is not the basis of our faith, and we are not under it.