The FBI argues that Orenstein looked at the question too broadly and focused on possible future abuse rather than the actual case he was considering. And then effectively accuses him of overreach by saying his ruling "goes far afield of the circumstances of this case and sets forth an unprecedented limitation on federal courts' authority.
That argument would seem to be self defeating: the first part says that it is only about this one individual device (case) and pretends no precedent would be set. The second part is a concern that a precedent has been set (albeit the opposite one to the one they wanted) by a judgment in the same particular case.