The 3rd branch is not just SCOTUS. It is the judiciary, which includes the FISA court.
Actually, I disagree in principle. The Supreme Court is the 3rd branch, as established by the Article III of the Constitution. The minor courts are a creation of Congress (under that same article) and are answerable to Congress for matters of scope and authority (and funding). I think in the full context of the matter at hand this IS an important distinction. In matters of Constitutionality, SCOTUS is the fat lady.