Rules on Eavesdropping

I also found this article on the New York Times Online website. I was completely unaware of this, but apparently governmental eavesdropping without court warrants is legal. In this situation, the eavesdropping is now being put under court supervision. But by making the eavesdroppers accountable to the court, American's privacy is supposed to be further protected than before.

Here are my questions:
When did this law about legal eavesdropping come about?
Were there not already privacy laws in place that would have put eavesdropping laws in violation of those laws?
Should Americans feel more protected now that these Senators are moving to put eavesdroppers at the mercy of the court?

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