Well an outside lineman going inside at the exterior knee or lower of a D lineman and holding on to their leg is illegal and in the case 76 Irwin did both, thus the holding penalty. That said had Buckner taken one more step to engage his targeted lineman it would have been a chop block. Both are damn dirty when done from the side where a defender can't see it coming! That tells me Buckner was abusing that line off the edge and they got dirty to stop him.....