Possession is nine-tenths of the law

Prov. If you actually possess something, you have a stronger legal claim to owning it than someone who merely says it belongs to him or her. Dana may say he owns this house, but we actually live in it, and possession is nine-tenths of the law.

something that you say which means that if you have something, it is difficult for other people to take it away from you It would be hard to ask for the piano back after they've had it for so long. Possession is nine-tenths of the law and all that.

Custody presumes ownership. The basis of this legal maxim that comes down from the 17th-century is the commonsense observation that if you have control of something, chances are better than average that it's yours. Lawyers term it a rebuttable presumption: ownership is recognized unless disproved by someone holding a more valid claim. The phrase started life as “possession is nine points of the law,” which referred to possession's satisfying nine out of eleven factors that constituted absolute ownership. However, “nine-tenths” entered popular usage to reflect the idea that custody is 90 percent of legal ownership.