Maybe “points of the law” relates to points on a compass -
“Before the Magnetic Compass was discovered, early map makers would draw a small 16 pointed circle on the map, and place an “N” to point to North. These were the 16 Cardinal Points from which the winds were thought to blow. This drawing was called a “Wind Rose.” When the magnetic compass came along, it was usually set on top of the Wind Rose pattern in order to help face the nautical chart in the proper direction. The wind rose started to become known as a COMPASS ROSE. Since the 1100’s, compass bearings have been split into 16 different directions”
In that scenario, 9 points of 16 becomes a little more than half - i.e. in this phrase possession = a slight presumption of ownership, not an overwhelming one.