Those aircraft owners who are involved (as much as is permitted) in the maintenance of their own aircraft might be interested in a case that came before the Transport Appeal Tribunal of Canada (TATC) in June 2018.
Every aircraft owner has bits of equipment on their aircraft that stop working on occasions. And few aircraft owners have the resources, time, or availability always to be able to fix whatever isn’t working before the next time they want to fly. How then can an aircraft owner tell if their aircraft is legal to fly when they know some piece of equipment isn’t working?