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You know, according to the current situation with the laws, they can. While Supreme Court have forbidden warrantless GPS tracking placed in or under vehicles, the current state of things regarding cell phone tracking is not that clear. In fact, if police needs to have the location data of the particular person, they can pay some fee to the mobile phone carrier and get that tracking data together with the phone call records as a bonus.
Still there might be some cases when mobile phone carrier would reject such police offering, yet they are really rare. It can be easily seen because police have special instructions on how to spy your phone and I guess they are using those instructions quite frequently. And according to those documents, mobile phone carriers are happy to help police officers to get the necessary information for the appropriate financial reward.
It is also worth mentioning that it is much easier for police to get a warrant for so called pen/trap than for an ordinary wiretap. Pen/trap allows law enforcement officers to record only numbers which were dialed from and to your cell phone. This warrant lasts for 60 days and they must not notify you at the end of it that such kind of surveillance was used.
So I suppose that you would like to have some protection against this illegal tracking, right? While you cannot block the pen/trap system, you can prevent police from tracking your cell phone location without the warrant, saving your privacy rights in that way for sure.