Cell phone companies have records of calls and locations (via tower records) that can provide a bonanza of data for law enforcement trying to see where someone (or their phone, at least) is at any given time, potentially for years.
The Supreme Court, in a narrow 5-4 decision, has decided that if the police want that data, they need to get a search warrant from a judge. Which, honestly, is not all that high of a burden, but it prevents fishing expeditions and casual use of such info.
Cops dislike search warrants, because they require arguing that there's a reason for them to search. This decision is a significant win for American privacy rights, without actually doing that much to slow legitimate law enforcement efforts.
Supreme court bans police access to phone records without a warrant | Law | The Guardian
I guess it's a sign of a popular post when the sex-spammers hit it hard. (Mutter mutter mutter.)
Let's see if they've lost interest.