possession is nine points of the law

Etymology
. Presumably derives from legal principle where the satisfaction of 10 (or at times 12) points legitimated ownership; hence “nine points of the law” (sometimes “eleven points of the law”) constituted close to full ownership. Derived from the early English property system, where the right to possession of property was endorsed by the king in the form of a writ. There were nine traditional writs granted by the King, and each of these nine writs represented the nine basic rights of property possession. These nine writs evolved into the nine original laws defining property ownership, hence the expression "possession is nine points in the law."

Listed in the form “Possession is nine points in the Law.” as a common saying in 1616 by Thomas Draxe, Adages 163.