She also rejected the argument that former FBI director James Comey's mention of a "very high" price equated to official disclosure that compelled a wider release. The information had to be more specific than that, according to the ruling. And while Comey noted that the tool was only effective against an iPhone 5c running iOS 9, the FBI could theoretically find a way to expand its usefulness or ask the developer to build a similar implementation. If the vendor is exposed, Judge Chutkan said, this could "hurt the FBI's future efforts to protect national security."

This isn't going to please privacy advocates concerned that the FBI has such power, especially as it might be maintaining this power solely through obscurity -- it might get into your phone only because an outside security researcher hasn't discovered the flaw yet. And is the theoretical future usefulness of the tool a good enough excuse to keep it under wraps? At the same time, it's hard to ignore the likelihood that any public disclosure would likely invite some kind of retaliation. The judge had to strike a difficult balance, and it's not necessarily clear that it's the right balance.