Hieshyn has the right of that one: The Incarnation, Crucixion and Resurrections chief accomplishments are correcting deep widespread misconceptions of the Law and opening the door to salvation for Gentiles (the latter only because the Jews rejected their own Messiah, though that was every bit as much part of the plan.) The Law is a description rather than definition of righteousness, the distinction being it was established as requirement yet perceived as guarantee. The latter is all the more inexplicable given that the Tanakh uniformly relates even its most holy protagonists transgressing the Law in one way or another throughout its length; the only exceptions of which I am aware are Enoch and Elijah, who were SO exceptional they ascended to heaven bodily rather than dying the natural death that awaits all sinful humans (i.e. all humans.)

All of Jewish history testifies mans inability to rigorously obey the Law, yet First Century Jews were somehow convinced doing so would grant them salvation (and never mind the myriad Torah sacrifices to atone for myriad sins; Yom Kippurs very existence is nothing more than a ceremony to annually do for Jews what Christ did for all on the Cross.) Yet if the Law is Pauls "schoolmaster," the lesson is unchanged irrespective carnal mans inability to rigorously observe it. "For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled." Last I checked, heaven and earth were still here.

That does not mean we should go out and murder false prophets, witches, gays, insubordinate children or anyone else. If you check those passages of the Tanakh they usually conclude with something like "in this way you will keep your country free from such evil," but the real message is evil shall exist for as long as carnal man, but that we have a remedy in Christ when we, as carnal men, succumb to evils temptation (i.e. not in their murder when OTHERS succumb to it.)

The Law defines evil at least as much as righteousness (Paul is very clear on that point in Romans 7; the Law is holy, but apart from Christ it is also lethal, because it convicts us of sin that sin might be revealed and repudiated AS sin, but salvation is and always has been by faith in the Redeemer from sin, not the Law, which by itself only kills carnal men.) The Law is no less valid nor more tenable since the Incarnation; all that is changed is that all men have a permanent remedy when transgressing it, rather than needing periodic pilgrimages to the temple for atonement sacrifices that merely prefigured the ultimate sacrifice.