There are responsibilities and obligations connected to owning and maintaining aircraft, which differ from those stipulated for aircraft pilots.
Links:
Aviation Act (external link) (External link)
EU Continuing Airworthiness Regulation (external link) (External link) – especially chapters B and C pertain to the owner, and chapters D and E to the person or organisation maintaining the aircraft. (Does not pertain to aircraft covered by national regulation, which must comply with national AIR series aviation regulations.)