Is there a proper way to confiscate bitcoins, perhaps?
What exactly do you mean by confiscate actually? If you mean something like freeze coins on the network, I don't think it's really possible. Freezing of addresses like you seen chains like USDT TRC 20 and so on is actually a function of what centralization is about just like your Money can get frozen by regular banks.
Other networks that allow it have a consensus rule but even with a soft fork it's still not allowed. The freeze option you may find in some wallets only applies to that seed access in that wallet if I took that same seed to another wallet I'll spend it flawlessly.