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A12 pass is intercepted at the B4 yard line by B23. B23's momentum carries him into the endzone, where he is downed. During B23's run, A13 blocks in the back at the B10 yard line. Spot of enforcement?

B4 yl

Momentum rule brings the ball back out to the B4.

I agree w/ B4 as well.

Have some around me saying goal line, and even 20yd line.

They might want to read the momentum exception.:confused:

Since the basic spot for this running play is the end of the run, the confusion you're encountering stems from uncertainty about where that is. Although the runner was downed in the EZ, by rule the end of the run is the spot of the catch/recovery when the momentum rule is in effect.

10-3-3: The end of the run is:

c. The spot of the catch or recovery when the momentum rule is in effect.

Agree with previous posts, but would ask the covering official if 9-3-5-b may have applied...
A player shall not clip or block an opponent in the back except: using hands and arms to contact an opponent above the waist in warding off a blocker, or when attempting to reach a runner, or catch or recover a loose ball which he may legally touch or possess.

just somethings else to think about.