Deadline scheduling part 1 — overview and theory

I'm surprised that the deadline scheduler doesn't preempt tasks that run over their declared run time, either immediately or at the point where they would interfere with other tasks making their deadlines. Preempting them immediately seems like it would be technically easy, since that's normal scheduler functionality, and like it would be necessary to meet the goal of having the fewest possible misses if the requested schedule is impossible, as well as penalizing the task that makes the schedule impossible.