This is because no human being can be considered right with God by [obeying] the requirements of a law. [Note: It is difficult to determine the exact sense in which "law" is used in these verses. It may be law generally, or the law of Moses specifically. See Bruce, pages 52-58]. For the knowledge of what sin is comes from the law of Moses.

For all those people [i.e., Gentiles] who have sinned without [knowing] the law of Moses will also be lost without [knowing] that law. And all those people [i.e., Jews] who have sinned under [the authority] of the law of Moses will be judged by [the requirements of] that law.

Or, do you not know, brothers, (I am talking to people who know how law works) that the law has authority over a person only as long as he lives? [Note: It is not clear whether this refers to Roman law or the law of Moses].

Now the practice of circumcision [i.e., the Jewish rite of identity, signifying the responsibility to observe the law of Moses] is worthwhile, providing you obey [the rest of] the law of Moses. But if you disobey the law, you might as well have never been circumcised.

Now we [all] know that everything the law says applies to those who are under [obligation to obey] that law, [Note: Here "the law" appears to refer to the Old Testament Scriptures generally, since Psalms and Isaiah are quoted. See verses 10-18]. This is so that the mouth of every objector may be stopped [i.e., from making excuses for his sin], and thereby bring the entire world under God's judgment [i.e., both Jews and Gentiles].

What shall we say then? Is the law of Moses sinful? Certainly not! For I would not have known what sin was if it had not been for the law. For [example]; I would not have known [what it meant] to covet [i.e., have a strong desire for what belongs to someone else] except that the law said [Ex. 20:17], "You must not covet."

but I see a different law [at work] in my body, waging [spiritual] warfare against the law in my mind. It brings me into captivity to the law of sin in my body.