And I disagree, because over the last 100+ years the 4th amendment has been hollowed out with exception, after exception so much so that anyone that believes the 4th amendment "single most powerful check on law enforcement power in our society" likely does not really support any checks on power at all.
Your belief that we have powerful checks on government power is clear you support a much larger and more intrusive government than I ever would, I see the government today as an unchecked dystopia novel, you think it is perfectly fine and balanced, that is more scary to me than government power. That we as a society have lost the very notion of what freedom actually is, that we has a society have come to accept the gilded cage as "freedom"
Beyond that, It comes down to the question of constitution interpretation as well. You believe the 4th amendment is silent here, you believe the FBI is operating under authorization of the 4th amendment because a law was violated, a law that seems to be protecting people that are violating the 4th amendment wholesale (the nsa), and ironic twist if I ever saw one.
You believe this because our Supreme Court has been derelict in the duty at uploading the plain and true meaning of the US Constitution for decades, you like many look to the Supreme Court for the meaning of the constitution, you have outsourced your thinking to this body, these people for whom we in society have placed on pedestal, and ironically in practice have given a title of nobility, something forbidden in the constitution.
“You seem to consider the judges as the ultimate arbiters of all constitutional questions; a very dangerous doctrine indeed, and one which would place us under the despotism of an oligarchy. Our judges are as honest as other men, and not more so. They have, with others, the same passions for party, for power, and the privilege of their corps.... Their power [is] the more dangerous as they are in office for life, and not responsible, as the other functionaries are, to the elective control. The Constitution has erected no such single tribunal, knowing that to whatever hands confided, with the corruptions of time and party, its members would become despots. It has more wisely made all the departments co-equal and co-sovereign within themselves.”
― Thomas Jefferson