Justifiability / Access to Courts
From Stone, et al. "Constitutional Law"
A number of devices require or permit federal courts not to hear certain issues. Most of these devices are, in whole or in part, an inference from article III, section 2, providing that the "Judicial Power shall extend" to enumerated "cases" and "controversies." This provision, it is often said, forbids the courts from invalidating legislative or executive action "merely" because it is unconstitutional. The courts may rule only in the context of a constitutional case.
This principle has a number of concrete implications. In general, it means that courts may not issue "advisory opinions."; may not decide "political questions"; must have before them someone with "standing," or some kind of personal stake in the controversy; and may not decide issues that are either "premature" or "moot."