possession is nine parts of the law

possession is nine parts of the law

Actually possessing or having custody of something represents a strong legal claim to it (more so than simply claiming ownership). She's arguing that the antique stopwatch rightfully belongs to her, but possession is nine parts of the law.
See also: law, nine, of, part, possession
Farlex Dictionary of Idioms.

possession is nine points/tenths/parts of the ˈlaw

(saying) if you already have or control something, it is difficult for somebody else to take it away from you, even if they have the legal right to it
See also: law, nine, of, part, point, possession, tenth
Farlex Partner Idioms Dictionary
See also:
  • possession is nine points/tenths/parts of the law
  • tenth
  • possession is nine-tenths of the law
  • possession is nine points of the law
  • be (one's) place (to do something)
  • be somebody's place to do something
  • have a thing for (something)
  • be somebody's man/woman
  • be (one's) man/woman
  • in control of