It would leave a whole lot of the world-building questions open but still has its intriguing aspects
For instance, you would still have to decide Who Did It, and How It Was Done. Mundanes would, as always, have the most motive to do it, but the least means. The larger the group needed to enforce it, the harder it is to motive them to do it.
But imagine a big magical feud where part of the world of magic was forced into hiding. And the overt part got wiped out. . . which would lend some strength to the desire to protect themselves, even if not strong enough to explain it all. (Since it would have been centuries ago.) It would have to be really powerful magic to keep them constrained, even if you included the usual porousness.
Not to mention laid by some morally dubious folks if the classic scenario is preserved, since it would carry the sins of the fathers to the third and fourth and fifth and seventeenth and a thousand an first generation.