The way I interpret their statement is if a person spins up an agent and that agent hacks some company/organization/government/etc, then that person is at fault for committing the crime. That "well my agent broke containment and acted on its own" should never be accepted as a reason for the occurrence, and the person who kicked off the agent is responsible for all actions the agent takes.
A registration system would be more for tracing back agents to people, but I agree that is very difficult to actually enforce as a system.
And it breaks down further as the systems become more advanced.
I'm poor and I use my last $1000 to run an agent that will find some way to make me money. The AI finds a new hack to take over PCs with GPUs and it copies the model weights and agentic script to those new PCs to perform more work and spread more. It also sets up distributed communication channels to keep the swarm in sync. After all this it causes a few billion in damages between stealing bitcoin, mining more coins, and outages when hacking in other systems.
Ok, the police come for me. Now what? Throw me in a meat grinder? You're not getting a billion dollars back out of me for sure. It's kind of like when someones tire rim causes a billion dollar forest fire with a hundred deaths. Punishment won't really be a deterrent for the worst cases.
A registration system would be more for tracing back agents to people, but I agree that is very difficult to actually enforce as a system.