Spearing - Test Part 1

[WyMike]

There is a question on Part 1 regarding whether the runner can 'spear'.

Outside of the fact I'd be hardpressed to make a spearing call on a runner putting his head down to bull his way through a LB, I can't find a definitive ruling on it.

Tonight at our assoc. meeting rule 2.39 was mentioned. "The intentional use of the helmet to punish an opponet."

I can't find a specific ruling deeming this is only for the D.

If a blocking lineman "butt-blocks" it is a foul. If the D leads with his head, it is a foul. Isn't a running back lowering his head and leading with it to "punish" a LB covered by the definition of "spearing".

Can someone point me to a rule?

WM