Originally Posted by needforspeed
How do they know one of the parties is a member of Al Qaeda? It's not like the publish a membership list with every ones name and address is it?
If they have any real evidence or even suspician - couldn't they get a warrant to monitor the calls?
You cant get a warrant for something you don't know is coming. A warrant is the proper way to go if you know what number the person is calling from. If a call comes in that is intercepted from a previously unknown line that reveals a terrorist plot, a warrant can only be obtained beforehand if the NSA had some sort of psychic ability.