Who has a right to challenge government eavesdropping on conversations between people in the United States and outside?

 The Supreme Court on Monday considered who has a right to challenge government eavesdropping on conversations between people in the United States and outside the country in a case touching on federal efforts to fight terrorism.
http://www.reuters.com/article/2012/10/29/us-usa-court-surveilla/nce-idUSBRE89S10H20121029