possession is nine points of the law

proverb 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 points of the law.

Actually holding something is better than merely claiming it. For example, When Karen told John he must return the sofa he'd borrowed, he said possession is nine points of the law . This term originally alluded to nine elements that would aid someone's lawsuit, among them a good lawyer, good witnesses, a good jury, a good judge, and good luck. In time, however, the term was used more for squatter's rights. [Late 1500s]

To hold or control something gives one a greater advantage than simply claiming ownership or control. This term dates from the late sixteenth century. An early appearance in print was in T. Draxe’s Bibliotheca Scholastica (1616): “Possession is nine points in the Law.” Later references sometimes put it at eleven points, but nine is what has survived. The nine points in question are: (1) a good purse (much money); (2) a good deal of patience; (3) a good cause; (4) a good lawyer; (5) good counsel; (6) good witnesses; (7) a good jury; (8) a good judge; and (9) good luck. With these advantages one is apt to win one’s case. Today, however, the term is used more in the sense of squatter’s rights—that is, “I have it; just try and take it away from me”—than in any strict legal sense.