I'm not arguing the rule, just the penalty. Maybe it makes no odds to him if he finishes as a DQ or say 5th with a time penalty, and in fairness at least "stay in the lane" is a clear rule, but a full DQ seems a bit harsh to me.Leaving the lane is completely out of order while the race is still going on - how would you set a time penalty.
load of ways you could apply a time penalty be a % of qual time or median time or 3 placer. you'd have to work out what makes sense.