NFL offsetting penalties/declined by rule

[BrendanP]

Memphis and Orlando in the AAF just now. There are two fouls on the play: illegal man downfield on the offense, roughing the passer on the defense. Instead of the penalties offsetting, the ineligible receiver penalty is "declined by rule" and the roughing the passer is enforced. I'm confused. Why don't these just offset?

[Legacy Zebra]

Because one is a 5 and one is a fifteen. The NFL has different rules for 5 vs 15 enforcements.

[BrendanP]

Follow up question: reading the relevant section of the NFL rulebook, it appears to note that a live ball foul by one team and a dead ball foul by the other still results in an offsetting penalty as long as it isn't a 5-and-15.

So as I recall seeing in an NCAA game earlier this season, A70 commits a facemask penalty and B20 commits a personal foul after the play. Both fouls are enforced so the yardage is a wash, but team A ends up with an automatic first down. In the NFL these just offset and the down is replayed?

[Kalle]

So as I recall seeing in an NCAA game earlier this season, A70 commits a facemask penalty and B20 commits a personal foul after the play. Both fouls are enforced so the yardage is a wash, but team A ends up with an automatic first down. In the NFL these just offset and the down is replayed?

Correct. NFL does not treat DB fouls differently from LB fouls, and any DB foul committed before the LB fouls have been completed would be part of the same set of fouls to be enforced.