A federal appeals court in Atlanta ruled that there is an expectation of privacy in cell tower location information, and therefor it is protected by the Fourth Amendment. This runs counter to other recent rulings that allow access to the information without a warrant under the Stored Communications Act.
The recent ruling relies on precedent from the 2012 Supreme Court decision in United States vs. Jones which stated that a warrant was required to place a tracking device on a suspects car. Phone records provide the same information, just with a different technical means.
This would not apply to intelligence gathering activities, nor would it prevent access to your location information with a warrant. It is a move to recognize that our personal information, about which we have real privacy interests, is increasingly existing in the networks of third parties. Laws that assume anything sensitive would be on paper and stored in your house or on your person are absurdly outdated.
For now this is only a local precedent. The issue will almost certainly end up in the Supreme Court at some point.