Back during the Bush administration, the United States Congress made one of its worst decisions ever. They passed the Patriot Act. One of the many odious provisions of that law allows the Federal Bureau of Investigation (FBI) to get any information they want on any person (American citizen or not) by simply issuing a "national security letter" to any telecommunications company. They issue these letters in-house, and it does not require the signature of any judge. In short, as long as the FBI claims it is a matter of "national security" they can get access to any information without any kind of warrant (and without any showing of probable cause).
This is clearly unconstitutional, since that document requires the government to show probable cause and get a warrant from a judge before it can seize any private or personal information from or about a citizen. But Congress was stupid enough to pass the Patriot Act, and the FBI (under both Bush and Obama) has used the law many times for warrantless searches. Back in 2007, the Justice Department's Inspector General said the FBI had committed widespread violations in their use of the "national security letters", and the FBI promised to tighten oversight of the system. But it is unknown whether they have stopped those violations (since the letters are issued in secret). I suspect they haven't though.
Recently they issued 19 of those letters for Google. But Google refused to cooperate. Unfortunately, U.S. District Judge Susan Illston sided with the FBI. She has ruled that Google must comply and turn over the information requested to the FBI, in spite of the fact that the FBI did not request or receive a warrant. This is very disappointing. Google was acting appropriately in trying to keep their customer's information secret. I hope they appeal this decision.
There is no reason why the FBI, and any other policing organization, cannot get a legal warrant if they have probable cause to believe a crime is being, or has been, committed. If they don't have probable cause, then they should not be able to get the information -- because they are just on a "fishing expedition", which is exactly the sort of thing the men who approved the Constitution were trying to prevent.
The Patriot Act is the biggest invasion of rights we have ever seen in this country. That odious law needs to be overturned -- either by the courts or by Congress.