[T]he Obama administration has argued that warrantless tracking is permitted because Americans enjoy no “reasonable expectation of privacy” in their–or at least their cell phones’.

CNET has the rest of the story at http://news.cnet.com/8301-13578_3-10451518-38.html

The question is not only whether the Fourth Amendment prohibits it, the question is where in the Constitution the Federal Government is given the power to do so and the answer is nowhere.