how can Americans be sure that the Agency does not invade their privacy?
Image: Photo of the Capital BuildingThe 4th Amendment of the Constitution demands it... oversight committees within all three branches of the U.S. government ensure it... and NSA employees, as U.S. citizens, have a vested interest in upholding it. Respecting the law is only a part of gaining Americans' trust.
http://www.nsa.gov/coremsgs/corem00003.cfm