Since the DMCA prohibits the circumvention of Access Controls, couldn't Apple litigate the heck out of the GreyKey?
> This section does not prohibit any lawfully authorized investigative, protective, information security, or intelligence activity of an officer, agent, or employee of the United States, a State, or a political subdivision of a State, or a person acting pursuant to a contract with the United States, a State, or a political subdivision of a State.
So it would probably go nowhere in court
On paper sure there's merit to it, in practice it's probably an exercise in futility while the exploit is un-patched and GreyKey is useful to law enforcement.