Article III of the U.S. Constitution limits the jurisdiction of federal courts to cases and controversies. Over the years, federal courts have construed the "case or controversy" requirement to encompass a number of subsidiary requirements. The case must not be moot. The controversy to be decided must be ripe for decision. So-called "political questions" are beyond the federal judicial power. And federal courts will not issue advisory opinions.
Traditionally, an advisory opinion was understood to represent a request that a court rule on the lawfulness of something before an actual case challenging that thing’s lawfulness featuring adverse parties was brought before the court. For example, the legislative branch may be considering whether to enact a statute that may present constitutional concerns. Some legislators may wish to obtain a court’s ruling on whether the proposed legislation could withstand constitutional challenge if it were to be enacted. That scenario would present a classic instance of an advisory opinion.
