moot point

noun2

1. •
   An issue that is subject to, or open for, discussion or debate, to which no satisfactory answer is found; originally, one to be definitively determined by an assembly of the people.

   • Exactly which of the songs on Small Change originated in London is a moot point. — 2009
2. •
   An issue hardly worth debating because it is no longer practically applicable.

   • Until we rebuild downtown, whether we build more parking spaces is a moot point.
   • Who really owned that horse is a moot point now that it has run away.