CLAIM: Paul writes that “sin is not imputed where there is no law.” Does this mean that God did not judge sin before the law was given?
RESPONSE: The issue here is not whether or not there was sin. After all, Paul writes that “sin was in the world.” The issue is how God judged sin during this time. When Paul says that sin “is not imputed,” he uses the Greek term ellogein. This refers to sending a bill and charging it to someone’s account (cf. Phile. 18). Thus according to Paul, sin wasn’t judged by the standard of the Mosaic Law.
Paul’s point is that even though people were less guilty, they weren’t any less dead. After all, people still died in this era of history. In the very next verse, Paul writes, “Nevertheless death reigned…” (v.14). Earlier in Romans, he writes, “All who have sinned without the Law will also perish without the Law, and all who have sinned under the Law will be judged by the Law” (Rom. 2:12). After all, the wages for sin is death (Rom. 6:23).
We see that “death reigned” throughout the book of Genesis. In Genesis 5, the evidence of the judgment for sin is the repeated refrain: “John Doe lived for so many years and he died… and he died… and he died…” This repetition in Genesis is evidence that God did judge sin before the Law of Moses. In very next verse, Paul writes, “Nevertheless death reigned…” God judged human evil in the Flood (Gen. 6:5-13) and at Sodom and Gomorrah (Gen. 19).
 Timothy Keller, Romans 1-7 For You (The Good Book Co., 2014), 125.