Previously, law enforcement needed to obtain a warrant prior to acquiring call location information. A recently passed bill changes that, although only for emergency situations.
In order to thus obtain such information without a warrant, there must be probable cause to believe that an emergency situation exists such that an individual faces risk of death or serious bodily injury, and the time to request a warrant would increase that risk. Then, within forty eight hours of obtaining such information, law enforcement must apply for a court order to keep that information, citing the probable cause to obtain it and also that the agency continues to have a bona fide reason to keep it. If the court does not side with law enforcement, then law enforcement would be required to destroy any information thus obtained.
For obvious reasons, this law has caused quite the stir and citizens are concerned about the possible implications.