Illegal Participation Spot of Enforcement

[Robert Goodman]

Originally Posted by HLin NC

9-6-1

But that just says for a running play, "basic spot". Does that mean it supersedes the all-but-one principle in case the foul was by the offense behind the basic spot?

Suppose a player of A returns to the field illegally at the 50 yard line during a down with no change of possession, then blocks an opponent at the B40, blocks another at the B30, all during the same run which ends at the B20. Is the penalty enforced automatically from the B20, or is it from one of those other spots?