Barty Crouch Jr.

Going by the age of the magic, I'd say the wards were put in place before any disowning, and long before the Protectorate, too. Blood magic of this nature has no regard for the law, and will answer only to those who cast it, or to their heirs. I don't know why Orion and Walburga never changed the spell themselves... perhaps they meant to but never got 'round to it.

I can think of one thing to try, but it's rather macabre. Especially so soon after her passing. And it might end up being nothing more than a hex in the dark.