Reply #3: In order to bring/sign on a lawsuit

[Mabus]

you have to have "standing". This means you have to be able to demonstrate to a court that you have been harmed.

1. Injury: The plaintiff must have suffered or imminently will suffer injury. The injury must be actual, imminent, distinct, and palpable, not abstract.
2. Causation: The injury must be fairly traceable to the defendant’s conduct.
3. Redressability: A favorable court decision must be likely to redress the injury. If you sue and win, the court can make an order that will help you.

In addition,
1. Prohibition of Third Party Standing: A party may only assert his or her own rights and cannot raise the claims of a third party who is not before the court.
2. Prohibition of Generalized Grievances: A plaintiff cannot sue if the injury is widely shared in an undifferentiated way with many people.
3. Zone of Interest Test: There are in fact two tests used by the United States Supreme Court for the Zone of Interest
a. Zone of Injury - The injury is the kind of injury that Congress expected might be addressed under the statute. Federal Election Commission v. Akins, 524 U.S. 11 (1998)
b. Zone of Interests - The party is within the zone of interest protected by the statute or constitutional provision.
http://www.answers.com/topic/standing-law