If the law was of no effect after the new covenant through Christ, Paul would never said that it was Spiritual, and holy and the commandment holy, just and good. I think you believe what Paul wrote don't you?
For what was impossible for the law in that it was weak through the flesh, God did by sending his own Son in the likeness of sinful flesh and concerning sin, he condemned sin in the flesh, in order that the requirement of the law would be fulfilled in us, who do not live according to the flesh but according to the Spirit. Romans 8:3-4
But now [Christ] has attained a more excellent ministry, by as much as he is also mediator of a better covenant which has been enacted upon better promises. For if that first [old] covenant had been faultless, occasion would not have been sought for a second [new covenant]. Hebrews 8:6-7