Remove the comma before "&"

Error²Federal courts, Illinois courts21st and 22nd editions

Authors' names take commas except the last, set off by an ampersand with no comma: “Ann Harlow, Ben Pemberton, Carla Ruiz & Dev Patel”, not “…, Carla Ruiz, & Dev Patel”.¹

1. 1R. 15.1(a) Two or three authors; R. 15.1(b) More than three authors; B15.1 Full Citation. Tables: T6 Case Names and Institutional Authors in Citations.
2. 2An error: the rule in note 1 allows one form, and this is not it.