Under the Law Vs. Outside the Law: Did Paul Nullify The Law?

What did Paul mean when he said that he is not “under the law, but under grace”? Many have understood it to mean that we no longer need to obey the commands given in the Torah. But is this what Paul is really saying? Paul speaks of reaching those who are “under the Law” and those who are “outside the Law” as two separate and different groups. Who are these groups of people, what it does it mean for believers in Yeshua, and how do we reach them?