National Public Radio reports that the FBI is still complaining about January's Supreme Court ruling that installing a GPS tracking device on a suspect's car without the owner's knowledge requires a warrant under the Fourth Amendment. The FBI said last month that it was forced to turn 3000 GPS devices off when the Supreme Court handed down its decision.

Yet NPR's reporting suggests the situation wasn't actually as dire as earlier reporting had suggested. NPR reports that the FBI "scrambled to get search warrants for weeks before the decision, working to convince judges they had probable cause to believe crimes were taking place." NPR says the government "still had to turn off 250 devices that they couldn't turn back on." In other words, they may have turned off 3,000 devices the day the Supreme Court issued its ruling, but they turned about 2,750 of them back on soon afterwards.

In Congressional testimony last month, FBI Director Robert Meuller said the ruling "will inhibit our ability" to do GPS tracking "in a number of surveillances where it has been tremendously beneficial." Mueller said that in cases where they didn't have probable cause, the FBI is forced to deploy teams of six to eight people to track suspects the old-fashioned way.

"If you require probable cause for every technique, then you are making it very, very hard for law enforcement," an FBI lawyer told NPR.

Of course, that's kind of the point. Law enforcement's job would be a lot easier if we just did away with the Fourth Amendment and gave the police unfettered spying powers. But that would open the door to abuses of power, so the founders wisely limited government searches to cases where the government could demonstrate it had probable cause to believe that a crime had been committed.

The fact that the FBI was able to get a warrant for more than 90 percent of the GPS devices it had in the field suggests the warrant requirement isn't too onerous. And in rare cases where a judge refuses to issue a warrant for tracking that's essential to an investigation, the FBI has the option to deploy its own resources to track suspects with human agents. The high costs of this option ensures that the FBI will use it sparingly. But that's a feature, not a bug.