PA-28 Cherokee/Archer/Dakota/Pillan/Warrior
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 2
Situational Awareness
Ground Excursion Runway
Flight Crew Regained Aircraft Control
Human Factors
Aircraft X was given the option for RWY 16L upon landing they veered off to the left edge of the runway ground pointed out the aircraft off the runway.  I saw the aircraft re-entering the runway just north of Golf and maneuvered back to the centerline and gave them instructions to turn left at the end and contact ground point seven.  Wind was light and variable at 4 kts.
Tower Controller reported an aircraft landing and going off the runway; then entering the runway again.