#1.) 1 John 3:4 "Whosoever committeth sin transgresseth also the law: for sin is the transgression of the law".
#2.) Romans 7:7 "What shall we say then? [is] the law sin? God forbid. Nay, I had not known sin, but by the law: for I had not known lust, except the law had said, Thou shalt not covet".
From this, we can deduce that the law refered to here, is the 10 commandments, as found in Exodus 20:3-17.......as the 10th commandment reads: "Thou shalt not Covet".
Psalms 19:7 "The law of the LORD [is] perfect, converting the soul: the testimony of the LORD [is] sure, making wise the simple".
Now, we know the Law in itself cannot save anyone, but it does tells us what sin is, which makes it ...a 'perfect' tool to show us our faults, which then should lead us to Jesus Christ, to ask forgiveness, for those things, wherein we have failed.