>The larger question, though, is not whether police should be required to obtain a warrant to access location data from cell phone service providers, but whether cell phone service providers should be providing this information to police without a warrant.

It's not really about whether they can provide this information to the police without a warrant. They can. The 4th Amendment doesn't protect against someone sharing your secrets voluntarily.

But this wasn't a voluntary sharing of information. It's done by a government order under the Shared Communications Act. Under current Court precedence this law is constitutional, but there are decent arguments was wrong when it decided that.