It would be treated just like a forced transfer would be treated today, depending on the jurisdiction. Which at least in some countries means that you would lose your house if the thief managed to sell it fast enough [1][2].
The control over the house, or majority of it, could be set to require multiple signatures, or require each transfer to have a forced delay.
If someone hits me with a rubber hose until I give them my private key, do they get to then keep my house?