3 U.S. Code § 4
3 U.S. Code § 4 is about Vacancies in electoral college. It is under Chapter 1 (Presidential Elections and Vacancies) of Title 3 (The President) of the Code.
Each State may, by law enacted prior to election day, provide for the filling of any vacancies which may occur in its college of electors when such college meets to give its electoral vote.