I have heard different answers to this one so let me know what you think. Since there is no 5 yard rule in High School can a defender basically block a receiver all the way down the field? I think no, but some have told me he can chuck him all the way down the field until the ball is in the air. According to rule 9-2-3d a defender cannot contact an eligible receiver who is no longer a potential blocker. Now I would let the defender basically chuck him off the line but I think once the receiver is on the same yard line as the defender he is then off limits and if the defender hits him before the ball is in the air we have illegal use of hands. Maybe I am making this harder than it should be so please help me out.

If he is at the same yard line and not moving towards the defender, he is no longer a potential blocker. Therefore, your ruling would be correct.

Sounds like you've got a pretty good understanding of the rule to me. The defense is allowed to contact the receiver as long as the contact is legal. If the receiver is turning away from or running past the defender, he is no longer a potential blocker. If the ball is in the air it is DPI.

"When he is no longer a potential blocker." A receiver is no longer a potential blocker once he goes downfield; consequently, a defender cannot chuck him.

There is some circular logic because a receiver who blocks would commit an OPI foul if, and only if, the ball is thrown beyond the LOS. Since the receiver cannot block legally, then the defender cannot block the receiver.