The matter is common sense. Do we in Christ think it's OK to murder now since He washed away our sins?
No, of course not. Even if one saved does murder after coming to Christ, would that one not be judged by a law? Aren't those who would call that law "man's law" just making excuse, since man got the judgments against murder from God? (Yes, even in America man's laws against murder originated from The Bible.)
Are those convicted of murder in prison immediately released if they turn to Christ Jesus and are baptized in Him? No, of course not. (Whether it helps the murderer get a parole later is a different subject.)
The preachers who teach that our Lord Jesus nailed all the law on His cross have grossly misunderstood what the law is for and about. Apostle Paul taught that IF we walk by The Spirit, then we are dead to the law; that doesn't mean all of God's laws were done away with. It means by walking in The Spirit we won't be doing anything against the law.
Gal 5:18-25
18 But if ye be led of the Spirit, ye are not under the law.
19 Now the works of the flesh are manifest, which are these; Adultery, fornication, uncleanness, lasciviousness,
20 Idolatry, witchcraft, hatred, variance, emulations, wrath, strife, seditions, heresies,
21 Envyings, murders, drunkenness, revellings, and such like: of the which I tell you before, as I have also told you in time past, that they which do such things shall not inherit the kingdom of God.
22 But the fruit of the Spirit is love, joy, peace, longsuffering, gentleness, goodness, faith,
23 Meekness, temperance: against such there is no law.
24 And they that are Christ's have crucified the flesh with the affections and lusts.
25 If we live in the Spirit, let us also walk in the Spirit.
KJV
Paul put an "if" there in his statement of Gal.5:18. An "if" presents a condition.
Rom 3:25
25 Whom God hath set forth to be a propitiation through faith in His blood, to declare His righteousness for the remission of sins that are past, through the forbearance of God;
KJV
What does "remission of sins that are past" mean? I thought Christ remits all our sin forever after we believe on Him and are baptized??? No! When we first come to Christ and believe, and are baptized in Him, all sin from that point backwards is forgiven.
In 1 John 1 we are shown that we need to repent of slip-ups that we make after... having come to Christ and baptized. That is one of the purposes of Holy Communion time we have with Jesus. Apostle Paul said let a man examine himself in that time of Communion (1 Cor.11:25-30).
1 John 1:8-10
8 If we say that we have no sin, we deceive ourselves, and the truth is not in us.
9 If we confess our sins, He is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.
10 If we say that we have not sinned, we make Him a liar, and His word is not in us.
KJV
The many 'hirelings' in today's Churches have corrupted this understanding by not properly teaching it like the Scripture actually is written. That's why so many brethren today think all they need do is believe and be baptized in Christ, and then no matter what they do afterwards they think they have no need to repent of it to Christ.