Many people point out that this type of tracking would only be possible if VPN companies handled logs to the Supreme Court, others say that patterns on the VPN connections could be detected and then the access to X be uncovered, at least partially (technically they only need to know you used X on a VPN, not what you saw on X or anything else). Others say that, besides logs, it is impossible to know if a citizen Y used X.
If you were, let's say, in the Supreme Court IT team and needed to detect who is using X through a VPN, how would you do it (besides asking the companies for the logs).