This is the law in Georgia that is being ignored by Raffensperger and Abrams, pointed out by John Fredericks:
Georgia Code Title 21. Elections § 21-2-501
(10) The run-off primary, special primary runoff, run-off election, or special election runoff shall be a continuation of the primary, special primary, election, or special election for the particular office concerned. Only the electors who were duly registered to vote and not subsequently deemed disqualified to vote in the primary, special primary, election, or special election for candidates for that particular office shall be entitled to vote therein, and only those votes cast for the persons designated as candidates in such run-off primary, special primary runoff, run-off election, or special election runoff shall be counted in the tabulation and canvass of the votes cast. No elector shall vote in a run-off primary or special primary runoff in violation of Code Section 21-2-224 .
https://codes.findlaw.com/ga/title-21-elections/ga-code-sect-21-2-501.html