Mootness

Here is how SCOTUS described the mootness doctrine (see casebook p. 93): "The usual rule in federal cases is that an actual controversy must exist at stages of appellate or certiorari review, and not simply at the date the action is commenced."


And here is how May & Ides describe the doctrine of mootness:

"The requirement that a case satisfy the requisites of justiciability applies from the outset of litigation up through the final stages of appellate review, including Supreme Court review. This means that during the entire federal litigation process, the parties must be and remain adverse to one another in the context of a judicially resolvable controversy. If at any time during the litigation process that adversity dissipates, the case will be deemed moot and dismissed. Stated slightly differently, the requirements of standing must be satisfied during the entire course of a litigation. If either the law or the facts change such that any one of the basic standing elements--injury-in-fact, causation, or redressability--is no longer satisfied, the mootness doctrine will be triggered."

The mootness doctrine addresses many of the same separation of power concerns as does the advisory opinion doctrine. How is mootness similar to the advisory opinion doctrine? How is it dissimilar?