Domains point to IPs, and IPs already have subpoenable ownership records at RIRs. In the real estate metaphor: we have property ownership records, but we don't have records of every rental tenancy.
This article is not inconsistent with my comment. The court rejected a subpoena against the ISP for the identity of the user of the IP, not against the RIR for the identity of the owner of the IP. This is like the court rejecting a subpoena against the landlord for their tenant's identity.
That's not true. Those are registration records NOT ownership records. People do not purchase ip address or domains. They register them for temporary use.
For non-legacy allocations, point taken (but my original comment still stands if you replace "ownership" with "registration"). For legacy allocations, it's more complicated.
