This is completely FALSE.
The New Testament makes it crystal clear that (1) Christians can and do sin, (2) Christians must deal with their present sins, and (3) failure to deal with present sins leads to serious consequences. This has nothing to do with "being under the Law" but it has everything to do with "being under Grace".
We should never represent the grace of God as either (a) a license to sin or as (b) an excuse to ignore our present sins. That is what false teachers like Joseph Prince teach, but as I have already quoted from the first epistle of John (1&2), I will quote it once again to show that JP is a liar and should not be trusted.
5 This then is the message which we have heard of him, and declare unto you, that God is light, and in him is no darkness at all.
6 If we say that we have fellowship with him, and walk in darkness, we lie, and do not the truth:
7 But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin.
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.
1 My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous:
2 And he is the propitiation for our sins: and not for ours only, but also for the sins of the whole world.
3 And hereby we do know that we know him, if we keep his commandments.
4 He that saith, I know him, and keepeth not his commandments, is a liar, and the truth is not in him.
5 But whoso keepeth his word, in him verily is the love of God perfected: hereby know we that we are in him.