Under Article III, Section 2 of the United States Constitution the jurisdiction of the Federal Courts extends to “cases” and “controversies.” This has been interpreted to mean that the Federal Courts do not have the power to resolve legal questions that do not arise out of an actual ‘live’ dispute between real parties.
One effect is that legal actions cannot be brought or continued after the matter at issue is “moot,” i.e., the dispute has been resolved, leaving no live dispute for the court. More significantly from an IP perspective, a suit cannot be brought if it is not “ripe,” i.e. before the challenged law, government action, or right has produced a direct threat to the party suing – and that party has to have “standing,” i.e., a genuine interest in the outcome.
From this “case or controversy” requirement comes the need for a clear threat of suit from a right holder against a party, (e.g., an accusation of patent infringement and threat to sue) before a declaratory judgment action can be brought. The requirement is also expressed as a prohibition on advisory opinions, i.e., the court cannot consider “what-if” cases, only actual disputes.