Ga. Code § 19-3-31
Notwithstanding any other law, in all counties having a population in excess of 400,000 according to the United States decennial census of 1990 or any future such census or in counties where the county site is located in an unincorporated portion of the county, the judge of the probate court or his or her clerk shall be authorized to issue the marriage licenses provided for by Code Section 19-3-30 and to take and perform any and all other actions prescribed in Code Section 19-3-30 either at the courthouse located at the county site or at any permanent satellite courthouse within the county which has been established and constructed by the governing authority of the county and has been designated by the governing authority of the county as a courthouse annex or by similar designation has been established as an additional courthouse to the courthouse located at the county site.
OCGA § 19-3-31