After reading a prior disussion by HeadAlphaGeek and after reading Redding's Study Guide, see Examples 10-16 on page 134 here is my question . While B is covering eligible receiver "A" and steps on the sideline as they run down the field. If "B" intercepts the forward pass thrown to "A" while inbounds. this would NOT become a foul for illegal participation but would be a legal play. "A" did not touch the ball and B was inbounds at the interception. ??