The same way someone from the time of Adam to Noah is guilty.
No law for them, yet God says they did evil. This is because they violated the law written in their conscience.
A knowledge of good and Evil is the same as a Law.
Romans 2: 11 For there is no partiality with God.
12 For as many as have sinned without the law will also perish without the law. As many as have sinned under the law will be judged by the law.
13 For it isn’t the hearers of the law who are righteous before God, but the doers of the law will be justified
14 (for when Gentiles who don’t have the law do by nature the things of the law, these, not having the law, are a law to themselves,
15 in that they show the work of the law written in their hearts, their conscience testifying with them, and their thoughts among themselves accusing or else excusing them)
He is probably referring to this -
Romans 5: 12 Therefore as sin entered into the world through one man, and death through sin; so death passed to all men, because all sinned.
13 For until the law, sin was in the world; but sin is not charged when there is no law.
14 Nevertheless death reigned from Adam until Moses, even over those whose sins weren’t like Adam’s disobedience, who is a foreshadowing of him who was to come.
I see Paul as making the point that even though the people from Adam to Moses were not violating a spoken law like Adam, they still suffered the consequences of Sin.
This can be explained in two ways -
Through the concept of original guilt- I e though no Sin was charged to these people, they were considered guilty for Adam’s Sin and thus punished.
Accept verse 2s claim that All sinned and hence died. Meaning that they violated some law. We find this law in the reference to the law written in the conscience mentioned in Romans 2.
I hold to the second interpretation as it is in line with Romans 2 which teaches that all people are charged with Sin irrespective of whether they were under the Law or not. And this is connected to the conscience.