Stiff-arm ?
 

A runner stiff-arms a defender by placing his hand on the face mask in such a way that the initial contact forces the defenders head back and up so that the defenders face is looking skyward. There is no grasping. The runner (a) takes his hand off immediately or (b) continues the contact so that the face of the defender stays looking skyward.

NF and NCAA.

Both are legal. There is not restriction on either level to my knowledge as to any stiff arm as long as they do not grasp the mask. The tackler can tackle around the helmet as long as they do not grasp the facemask or openings. The only rule I can think of that is illegal with the helmet is blocking near the helmet or using the helmet as a battering ram.

Peace

I can only answer for how I've been taught to rule on this with NCAA Rules (which we use here in Europe). It is either nothing (ie legal) or it is a Personal Foul. You have to decide if the contact by the runner was so fierce that you would call it a PF for striking a blow.

That is the way I rule it as well. The runner is permitted to continuously contact an opponent's facemask so no foul unless he delivers a striking blow first.

For a striking blow could you consider this a punch and toss the kid or would it just be a 15 yard PF. I have been thinking about this for a while. What if this striking blow was the cause of a fight and this was the only blow that he threw.