Kurt Ullman wrote:

Even then no one has been able to tell me why that is illegal. Wire
taps that are legal can monitor both sides of the conversation when
one of the phones is tapped legally. If Mobster 1's phone is legally
tapped, then it is perfectly legal to listen in when Mobster 2 calls
and anything M2 says can be used legally.
Since there are no US law related restrictions on intercepting
communications outside the US then as long as the phone call or
communication starts outside the US, it would be the same as M2
calling M1, even if it is international. Communications STARTING with
in the US would be different.

And even if both sides of the conversation are inside the U.S., the
president, under his Article II powers, can listen. Only those charged or
suspected of a crime are protected by the 4th Amendment. Enemy soldiers are
not protected. Unlawful enemy combatants (sabateurs, guerrilas, etc.) are
not protected. People posting critical comments on newsgroups are not.