Illegal block

[cowbyfan1]

This may have been brought up before but here it goes anyways.
Play. Center snaps the ball, lineman reaches out and grabs the back of the defensive linemans head (not the edge) and pulls/pushes him to the ground by the head.

Illegal block? And if not why?

I say it is illegal as rule 2-3 says the block must be from the shoulders down, but we have others around here that says it is not.