Local Government Code §150.021

(a) A municipality may not require residency within the municipal limits as a condition of employment with the municipality. A municipality may require residency within the United States as a condition of employment. (b) The prohibition under Subsection (a) does not apply to residency requirements for: (1) candidates for or holders of a municipal office, including a position on the governing body of the municipality; or (2) municipal department heads appointed by the mayor or governing body of the municipality. (c) The governing body of a municipality may prescribe reasonable standards with respect to the time within which municipal employees who reside outside the municipal limits must respond to a civil emergency. The standards may not be imposed retroactively on any person in the employ of the municipality at the time the standards are adopted.