Settle the argument
Is motion allowed in flag football?
Yes. One player, not toward the goal line.
One offensive player can be in motion at the snap, moving sideways or backward. Moving toward the opponent’s goal line at the snap is illegal motion.
If two or more players are moving when the ball is snapped, that’s an illegal shift.
The rule
IFAF Flag Football Rules 2023, R 7-1-3-d
The call
S19 False start, illegal procedureRoll the forearms in front of the chest.
Illegal motion or shift: 5 yards from the line of scrimmage (signal S19).

Other rulebooks
NFL FLAG and local leagues can differ. Check the rulebook your league plays.
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