Generally, IPv6 does autoconfiguration (never seen a home router with DHCPv6), so no need to ask for anything. Even for ipv4, I've never seen a home router enforce DHCP (even though it would force the public ip).
But the point stands, you can't selectively punish a single device, you have to cut off the whole block, which may include well-behaved devices.
But the point stands, you can't selectively punish a single device, you have to cut off the whole block, which may include well-behaved devices.