Federation rules. 1st and 10 on A's 25. A32 runs to A's 30 where B24 attempted to tackle him. A32 stiff arms B24 with his hand contacting the face mask of B24.

Is this a face mask penalty against A32?

Can the runner on a stiff arm facemask his opponent?

If it is a face mask, would it be 5 or 15 yards?

I'm sure there will be lots of screaming for a penalty from the sideline, but simply stiff-arming his opponent would not be a foul by A32, even if he contacts the facemask.

The foul occurs only if he GRASPS the facemask. At that point, the covering official would make a judgement as to the severity of the grasping and determine whether to assess a 5- or a 15-yard penalty.

So, to answer your questions:

Not necessarily;

Yes;

Could be either.

Middleman

Enforcement
 

Would this be marked off from the spot of the foul,if it occured behind the end of the run, and replay the down?

Re: Enforcement
 

Yes, the penalty for this foul would be enforced according to the all-but-one principle. If the runner continues to advance after the foul, the enforcement spot will be the spot of the foul. If the runner is stopped there or subsequently loses ground, the penalty will be enforced from the end of the run. Replay the down.