0
It means that ownership is easier to maintain if one has possession of something, or difficult to enforce if one has not
inferring that ownership is the (important) tenth point.
The expression you're referring to is actually
"Possession is 9 tenths of the law" or 9/10.
Nine Points of the Law - 1922 is rated/received certificates of:
USA:Passed (National Board of Review)
9 Points/Parts of the Law that Possession is