The summit of Broad Law is also the highest point (county top) of the historic county of Peeblesshire. It is also sometimes (erroneously) given as the county top of Selkirkshire. This is because in 1891, the area of Megget (a detached part of Lyne parish in Peeblesshire) was transferred to Yarrow parish in Selkirkshire. The administrative county boundary of Peeblesshire and Selkirkshire thus temporarily crossed Broad Law summit between 1891 and 1974. However, the historic county boundary remained several km to the east, where Dun Rig is the county top of Selkirkshire.