This question popped up during a session at the state meeting and a conflicting answer was given.
Is it a foul for a horse collar tackle if the runner does not go completely to the ground? The pull down is abrupt and the knees buckle but the runner is able to regain his balance and continue running. The answer given at the state meeting was he had to be tackled to the ground. I believe there is an NCAA bulletin that addressed this, but I haven't found it yet, but for Texas we do have our own philosophies. Straight from the mechanics manual under the officiating philosophies:
"To have a Horse Collar Tackle the runner does not have to be tackled. If the immediate
action buckles the runner’s knees but he is strong enough to fight through the action it is
still a foul."