ArsTechnica has a nice article on a recent ruling by the US Fifth Circuit court of appeals.
In this 2-1 decision, the court ruled that cellular location information is not covered by the fourth amendment, and does not require a warrant. The logic behind this ruling is that the information is part of business records created and stored by the mobile phone carriers in the ordinary course of their business.
Therefor, the data actually belongs to the phone company, and not to you. The Stored Communications Act says that law enforcement must get a warrant to obtain the contents of communications (the body of emails or the audio of a phone call) but not for meta-data like sender, recipient, or location.
The court suggests that if the public wants privacy of location information that they should demand (I suppose through market forces) that providers delete or anonymize the location information, and that legislation be enacted to require warrants for access to it. Until then, they say we have no expectation of privacy in that information.
The Fifth Circuit covers Louisiana, Mississippi, and Texas.
This ruling conflicts with a recent New Jersey Supreme Court, which unanimously ruled that law enforcement does not have that right, which ruling only applies in New Jersey.
Montana has a law requiring a warrant to obtain location information, while in California a similar bill was vetoed.
It seems very likely that one or more of these cases will go to the supreme court.