For a quick explanation of this case and its implications, go read Ed Brayton's Dispatches from the Culture Wars post of the 19th, entitled, "Kiss the Constitution Goodbye":
I cannot imagine that the SCOTUS could possibly allow the Executive Branch to hide illegal behavior. Such a ruling is so contrary not only to past SCOTUS rulings, but to the very purpose for the Court's existence. In the past, the Court has acted as a brake on the government, a bulwark against government misbehavior and oppression. That is the reality of why it exists as a third, independent Branch of Government, so it can rule against such overreaching activity and have a hope of it being obeyed. That is why it has the power to completely overrule and kill an act of Congress that has been signed into law by the President. That is why it is the only Branch that can, by itself, overrule the other two Branches in a way that would require a Constitutional amendment to be itself overridden! Yet, the Court has completely let us down, in one of the most important cases in recent memory. In this one ruling, without even hearing the specifics of the case, the SCOTUS has virtually destroyed the accountability of the Executive Branch of the Federal Government. This is a hole big enough to drive a whole army through, much less a Mack Truck.
The only way I can imagine this to happen is through the current conservative majority on the court, which just happens to include 5 catholic members.
Now I don't for a minute blame this on the RCC, or on these five Justices' religious beliefs. It IS on account of their conservatism, however, and I think this is a clear indication of how we can expect the Conservatives to act if and when they become a majority of this government, given how the Republicans have acted on their own in the House since obtaining a majority there.
Will this really mean the end of the Constitution's protections? By itself, I don't think so. A vast majority of people brought before the bar of justice on this country are brought before State and local courts, where it is unlikely that any State Secrets will be at issue. I would also doubt that many of the Federal actions would also fail to rise to that level, either.
But this IS a bad ruling, contrary to the very principles enshrined in the Constitution, that the Government cannot use illegal actions against citizens where those citizens' freedom or welfare is at stake. It allows the Government to continue its bad behavior, without the brake of Court oversight.
Hopefully, in time, a more liberal court will reverse this travesty.