Double Foul with "Dirty Hands"
 

I'm drawing a blank here. 3rd & 8 on A's 35. B is guilty of holding before the pass. B intercepts at the 50 and A commits a 15 yard facemask when they tackle him at A's 40. Do you enforce both penalties or do they offset?

This is the classic offsetting situation where there is a change of possession. This would have been offsetting had there been no change of possession as well. On a change of possession A would foul prior to the COP and B decline it to keep the ball.

The only time you enforce both would be if one was USC or a dead-ball foul.

In these scenarios where B gets the ball with dirty hands, all live ball fouls committed by A will cause an offsetting situation whether A's foul was committed before or after the change of possession.

Canadian Ruling
 

In cases where the first foul is not UR or RP, dual fouls are penalized from spot of first foul. A's best option is to keep the ball, 3D/13 @ A-30.

JugglingReferee, I don't follow that. Spot of the first foul? I thought these would offset since they were both live ball fouls and not USC.

Look at the header of my reply - it is for the Canadian amateur game.

People don't often reply, but I am sure that it does provide an interesting view into another facet of football.